Primer on Smell In addition to bringing out1 the flavor of food， what does the sense of smell do for us ? Smell “gives us information about place， about where we are，” says Randall Reed， a Johns Hopkins University professor whose specialty is the sense of smell. ___1___ “Whether we realize it or not， we collect a lot of information about who is around us based on smell，” says Reed. Even at a distance， odors can warn us of2 trouble — spoiled food， leaking gas， or fire. “It’s a great alert，” offers Donald Leopold， a doctor at Johns Hopkins. For example， if something in the oven is burning， everyone in the house knows it. With just a simple scent， smell can also evoke very intense emotion. Let’s say， for example， that the smell is purple petunias. ___2___ Now let’s imagine that your mother died when you were three， and she used to have a flower garden. You wouldn’t need to identify the smell or to have conscious memories of your mother or her garden. You would feel sad as soon as you smelled that spicy odor. Compared with3 animals， how well do people detect smelts ? That depends on what you mean by “how well”. We are low on receptor cells ： current estimates say that humans have roughly five million smell-receptor cells， about as many as a mouse. ___3___ Reed says that， across species， there is a relatively good correlation between the number of receptor cells and how strong the sense of smell is. “You can hardly find the olfactory bulb in a human brain —— it’s a pea-sized object. In a mouse， it’s a little bigger. It’s bean-sized in a rat， about the size of your little finger in a rabbit， and the size of your thumb in a bloodhound.” Does that mean that our sense of smell is not very acute ? Not exactly. While we may not have the olfactory range of other creatures， the receptors we do have are as sensitive as those of any animal. ___4___ A trained “nose”， such as that of a professional in the perfume business， can name and distinguish about 10，000 odors. Reed says that a perfume expert can sniff a modem scent that has a hundred different odorants in it， go into the lab， and list the ingredients. “In a modest amount of time， he comes back with what to you or me would smell like a perfect imitation of that perfume. It’s amazing.” What happens to4 our sense of smell as we age ? Many people continue to have good olfactory function as they get older. ___5___ Leopold says that smell is generally highest in childhood， stays the same from the teens through the 50s， and drops starting at about 60 for women and 65 for men. “The average 80-year-old is only able to smell things half as well as the average 20-year-old，” says Leopold. 词汇： scent /sent/ n. 气味，香味 petunia /p 'tju:ni / n. 喇叭花 olfactory / l'f kt( )ri/ adj. 嗔觉的，味道的 sniff /snif/ v. 嗅，闻，用力吸 注释： 1. bring out：使……显出，使……变得明显 2. warn of：发出关于……的警告。warn sb. of sth.：警告某人某事 3. compare with：与……相比 4. happen to：发生于，发生在 练习： A These flowers have a rich spiciness that no other petunia has. B Odors， or smells， can warn us about trouble. C That’s not the rule， however. D And smell tells us about people. E We can also think， and we make conscious (and successful) efforts to tell the difference between one smell and another. F A rat has some 10 million， a rabbit 20 million， and a bloodhound 100 million.

The Sahara Desert is the largest desert in the wld. It stretchesacross Africa from Senegal to Egypt. The Sahara Desert is an unfriendlyenvironment. During the day it's very hot， at night it’s sometimesvery cold. It is also difficult to find water in the Sahara. In 2006， Kevin Lin， Ray Zahab， Charlie Engle decided to dosomething very difficult. They made the decision to run across the SaharaDesert 4，300 miles (6，920km). It seemed impossible to do， but they wanted to try.The three men liked to test themselves， this would be a very big test. On the mning of November 2， Kevin， Ray， Charlie started theirtrip across the Sahara. Every mning they began running at 5:00. At11 a.m.they stopped rested until 5 p.m. Then they ran again until 9:30 in theevening. Each day they ran about 40 miles (64 km). Every day it was the samething. They got up ran. They listened to music on their iPods， they ran ran. Kevin， Ray， Charlie needed to eat a lot of food during theirtrip. Most people need about 2，000 calies of food each day. Kevin， Ray， Charlie needed between 6，000 9，000 calies every day. That's a lot offood! They also needed to drink a lot of water. The three men had some problems on their trip， many times theywanted to quit go home. It was often very hot (140°F/60°C) duringthe day， the heat made them sick. Their legs feet hurt. Sometimes itwas very windy， they couldn't see. One time they got lost. But they didn'tquit. After 111 days， Kevin， Ray; Charlie successfully finished their tripacross the Sahara Desert. They hugged each other put their hs in thewater of the Red Sea. Then they ran to a hotel to take a long shower. 　　词汇： stretch v. 延伸，伸展 calie n. 卡(路里)，小卡，大卡 quit v. 停止，放 　　注释： 1. ... made the decision to run across ...：......决正跑步横跨...... 　　练习： 1. It’s not always hot m the Sahara Desert.

The Sahara Desert is the largest desert in the wld. It stretchesacross Africa from Senegal to Egypt. The Sahara Desert is an unfriendlyenvironment. During the day it's very hot， at night it’s sometimesvery cold. It is also difficult to find water in the Sahara. In 2006， Kevin Lin， Ray Zahab， Charlie Engle decided to dosomething very difficult. They made the decision to run across the SaharaDesert 4，300 miles (6，920km). It seemed impossible to do， but they wanted to try.The three men liked to test themselves， this would be a very big test. On the mning of November 2， Kevin， Ray， Charlie started theirtrip across the Sahara. Every mning they began running at 5:00. At11 a.m.they stopped rested until 5 p.m. Then they ran again until 9:30 in theevening. Each day they ran about 40 miles (64 km). Every day it was the samething. They got up ran. They listened to music on their iPods， they ran ran. Kevin， Ray， Charlie needed to eat a lot of food during theirtrip. Most people need about 2，000 calies of food each day. Kevin， Ray， Charlie needed between 6，000 9，000 calies every day. That's a lot offood! They also needed to drink a lot of water. The three men had some problems on their trip， many times theywanted to quit go home. It was often very hot (140°F/60°C) duringthe day， the heat made them sick. Their legs feet hurt. Sometimes itwas very windy， they couldn't see. One time they got lost. But they didn'tquit. After 111 days， Kevin， Ray; Charlie successfully finished their tripacross the Sahara Desert. They hugged each other put their hs in thewater of the Red Sea. Then they ran to a hotel to take a long shower. 　　词汇： stretch v. 延伸，伸展 calie n. 卡(路里)，小卡，大卡 quit v. 停止，放 　　注释： 1. ... made the decision to run across ...：......决正跑步横跨...... 　　练习：7. On their trip across the desert: the three men ran through fivecountries.

The Sahara Desert is the largest desert in the wld. It stretchesacross Africa from Senegal to Egypt. The Sahara Desert is an unfriendlyenvironment. During the day it's very hot， at night it’s sometimesvery cold. It is also difficult to find water in the Sahara. In 2006， Kevin Lin， Ray Zahab， Charlie Engle decided to dosomething very difficult. They made the decision to run across the SaharaDesert 4，300 miles (6，920km). It seemed impossible to do， but they wanted to try.The three men liked to test themselves， this would be a very big test. On the mning of November 2， Kevin， Ray， Charlie started theirtrip across the Sahara. Every mning they began running at 5:00. At11 a.m.they stopped rested until 5 p.m. Then they ran again until 9:30 in theevening. Each day they ran about 40 miles (64 km). Every day it was the samething. They got up ran. They listened to music on their iPods， they ran ran. Kevin， Ray， Charlie needed to eat a lot of food during theirtrip. Most people need about 2，000 calies of food each day. Kevin， Ray， Charlie needed between 6，000 9，000 calies every day. That's a lot offood! They also needed to drink a lot of water. The three men had some problems on their trip， many times theywanted to quit go home. It was often very hot (140°F/60°C) duringthe day， the heat made them sick. Their legs feet hurt. Sometimes itwas very windy， they couldn't see. One time they got lost. But they didn'tquit. After 111 days， Kevin， Ray; Charlie successfully finished their tripacross the Sahara Desert. They hugged each other put their hs in thewater of the Red Sea. Then they ran to a hotel to take a long shower. 　　词汇： stretch v. 延伸，伸展 calie n. 卡(路里)，小卡，大卡 quit v. 停止，放 　　注释： 1. ... made the decision to run across ...：......决正跑步横跨...... 　　练习：6. Luckily， they never got lost.

The Sahara Desert is the largest desert in the wld. It stretchesacross Africa from Senegal to Egypt. The Sahara Desert is an unfriendlyenvironment. During the day it's very hot， at night it’s sometimesvery cold. It is also difficult to find water in the Sahara. In 2006， Kevin Lin， Ray Zahab， Charlie Engle decided to dosomething very difficult. They made the decision to run across the SaharaDesert 4，300 miles (6，920km). It seemed impossible to do， but they wanted to try.The three men liked to test themselves， this would be a very big test. On the mning of November 2， Kevin， Ray， Charlie started theirtrip across the Sahara. Every mning they began running at 5:00. At11 a.m.they stopped rested until 5 p.m. Then they ran again until 9:30 in theevening. Each day they ran about 40 miles (64 km). Every day it was the samething. They got up ran. They listened to music on their iPods， they ran ran. Kevin， Ray， Charlie needed to eat a lot of food during theirtrip. Most people need about 2，000 calies of food each day. Kevin， Ray， Charlie needed between 6，000 9，000 calies every day. That's a lot offood! They also needed to drink a lot of water. The three men had some problems on their trip， many times theywanted to quit go home. It was often very hot (140°F/60°C) duringthe day， the heat made them sick. Their legs feet hurt. Sometimes itwas very windy， they couldn't see. One time they got lost. But they didn'tquit. After 111 days， Kevin， Ray; Charlie successfully finished their tripacross the Sahara Desert. They hugged each other put their hs in thewater of the Red Sea. Then they ran to a hotel to take a long shower. 　　词汇： stretch v. 延伸，伸展 calie n. 卡(路里)，小卡，大卡 quit v. 停止，放 　　注释： 1. ... made the decision to run across ...：......决正跑步横跨...... 　　练习：5. Sometimes they couldn't see the road because it was windy.

The Sahara Desert is the largest desert in the wld. It stretchesacross Africa from Senegal to Egypt. The Sahara Desert is an unfriendlyenvironment. During the day it's very hot， at night it’s sometimesvery cold. It is also difficult to find water in the Sahara. In 2006， Kevin Lin， Ray Zahab， Charlie Engle decided to dosomething very difficult. They made the decision to run across the SaharaDesert 4，300 miles (6，920km). It seemed impossible to do， but they wanted to try.The three men liked to test themselves， this would be a very big test. On the mning of November 2， Kevin， Ray， Charlie started theirtrip across the Sahara. Every mning they began running at 5:00. At11 a.m.they stopped rested until 5 p.m. Then they ran again until 9:30 in theevening. Each day they ran about 40 miles (64 km). Every day it was the samething. They got up ran. They listened to music on their iPods， they ran ran. Kevin， Ray， Charlie needed to eat a lot of food during theirtrip. Most people need about 2，000 calies of food each day. Kevin， Ray， Charlie needed between 6，000 9，000 calies every day. That's a lot offood! They also needed to drink a lot of water. The three men had some problems on their trip， many times theywanted to quit go home. It was often very hot (140°F/60°C) duringthe day， the heat made them sick. Their legs feet hurt. Sometimes itwas very windy， they couldn't see. One time they got lost. But they didn'tquit. After 111 days， Kevin， Ray; Charlie successfully finished their tripacross the Sahara Desert. They hugged each other put their hs in thewater of the Red Sea. Then they ran to a hotel to take a long shower. 　　词汇： stretch v. 延伸，伸展 calie n. 卡(路里)，小卡，大卡 quit v. 停止，放 　　注释： 1. ... made the decision to run across ...：......决正跑步横跨...... 　　练习：4. They sometimes felt sick because it was so hot.

The Sahara Desert is the largest desert in the wld. It stretchesacross Africa from Senegal to Egypt. The Sahara Desert is an unfriendlyenvironment. During the day it's very hot， at night it’s sometimesvery cold. It is also difficult to find water in the Sahara. In 2006， Kevin Lin， Ray Zahab， Charlie Engle decided to dosomething very difficult. They made the decision to run across the SaharaDesert 4，300 miles (6，920km). It seemed impossible to do， but they wanted to try.The three men liked to test themselves， this would be a very big test. On the mning of November 2， Kevin， Ray， Charlie started theirtrip across the Sahara. Every mning they began running at 5:00. At11 a.m.they stopped rested until 5 p.m. Then they ran again until 9:30 in theevening. Each day they ran about 40 miles (64 km). Every day it was the samething. They got up ran. They listened to music on their iPods， they ran ran. Kevin， Ray， Charlie needed to eat a lot of food during theirtrip. Most people need about 2，000 calies of food each day. Kevin， Ray， Charlie needed between 6，000 9，000 calies every day. That's a lot offood! They also needed to drink a lot of water. The three men had some problems on their trip， many times theywanted to quit go home. It was often very hot (140°F/60°C) duringthe day， the heat made them sick. Their legs feet hurt. Sometimes itwas very windy， they couldn't see. One time they got lost. But they didn'tquit. After 111 days， Kevin， Ray; Charlie successfully finished their tripacross the Sahara Desert. They hugged each other put their hs in thewater of the Red Sea. Then they ran to a hotel to take a long shower. 　　词汇： stretch v. 延伸，伸展 calie n. 卡(路里)，小卡，大卡 quit v. 停止，放 　　注释： 1. ... made the decision to run across ...：......决正跑步横跨...... 　　练习：3. In the dle of the day: the men usually stopped running.

The Sahara Desert is the largest desert in the wld. It stretchesacross Africa from Senegal to Egypt. The Sahara Desert is an unfriendlyenvironment. During the day it's very hot， at night it’s sometimesvery cold. It is also difficult to find water in the Sahara. In 2006， Kevin Lin， Ray Zahab， Charlie Engle decided to dosomething very difficult. They made the decision to run across the SaharaDesert 4，300 miles (6，920km). It seemed impossible to do， but they wanted to try.The three men liked to test themselves， this would be a very big test. On the mning of November 2， Kevin， Ray， Charlie started theirtrip across the Sahara. Every mning they began running at 5:00. At11 a.m.they stopped rested until 5 p.m. Then they ran again until 9:30 in theevening. Each day they ran about 40 miles (64 km). Every day it was the samething. They got up ran. They listened to music on their iPods， they ran ran. Kevin， Ray， Charlie needed to eat a lot of food during theirtrip. Most people need about 2，000 calies of food each day. Kevin， Ray， Charlie needed between 6，000 9，000 calies every day. That's a lot offood! They also needed to drink a lot of water. The three men had some problems on their trip， many times theywanted to quit go home. It was often very hot (140°F/60°C) duringthe day， the heat made them sick. Their legs feet hurt. Sometimes itwas very windy， they couldn't see. One time they got lost. But they didn'tquit. After 111 days， Kevin， Ray; Charlie successfully finished their tripacross the Sahara Desert. They hugged each other put their hs in thewater of the Red Sea. Then they ran to a hotel to take a long shower. 　　词汇： stretch v. 延伸，伸展 calie n. 卡(路里)，小卡，大卡 quit v. 停止，放 　　注释： 1. ... made the decision to run across ...：......决正跑步横跨...... 　　练习：2. Each day the men ran f approximately eight hours.

Time to Stop Traveling by Air 　　Twenty-five years ago a young British man called Mark Ellingham decided that he wanted a change of scenery. So he went to Australia， stopping off in many countries between. He also decided to write about the experience and produced a guide for other travelers making similar journeys. 　　In 1970， British airports were used by 32million people. In 2004， the figure was 216 million. In 2030， according to government forecasts， it will be around 500 million. It's a growth driven by the emergence of low cost airlines， offering access to all parts of the world for less than ￡100. 　　This has made a huge contribution to global warming. One return flight from Britain to the US produces the same carbon dioxide(二氧化碳)as a year's motoring(驾车). A return flight to Australia equals the emissions(排放)of three average cars for a year. And the pollution is released at a height where its effect on climate change is more than double that on the ground. 　　Mark Ellingham built his business on helping people travel. Now he wants to help people stop – at least by air. 　　He is calling for a ￡100 green tax on all flights to Europe and Africa， and ￡250 on flights to the rest of the world. He also wants investment to create a low-carbon economy， as well as a halt to airport expansion. 　　Mark Ellingham's commitment is important because his readers aren't just the sort of young and adventurous people who would happily jump on a plane to spend a weekend exploring a foreign culture. They are also the sort of people who say they care about the environment. It's a debate that splits people down the middle. 　　The tourist industry has responded by offering offsetting(补偿)schemes. A small increase in the price of a ticket is used to plant trees. 　　But critics say that it is not enough to just be carbon neutral. We should be actively cutting back on putting green house gases into the atmosphere. And for the average person， making a plane journey will be his or her largest contribution to global warming. It maybe good to repair the damage we do. But surely it is better not to do the damage in the first place. 文章(1~7) Mark Ellingham spent quite a few days in China on his way to Australia 25 years ago.

Traveling from Britain to any other part of the world may cost you less than ￡100.

A round trip flight from Britain to Australia produces the same amount of carbon dioxide as three average cars do in a year.

Mark Ellingham has never hesitated to encourage people to travel by air.

Mark Ellingham's readers are not interested in environmental protection.

Critics argue that the best way to protect our environment is not to do any damage to it.

Mark Ellingham will collaborate with the critics in his efforts to fight global warming.