Unit 1 Festivals around the world Reading课时作业

一 、阅读理解（共 15 小题，每题 2 分，满分 30 分） 阅读下列短文，从每题所给的四个选项中选出最佳答案

　　Travel is exciting and summer is a busy period for holiday travel. Many people will travel great distances in airplanes, cars or other vehicles. Experts say people should know about other health problems that can strike when traveling by air.

　　One of these is a condition called hypoxia ( 缺氧症 ). It results from a lack of oxygen to the brain. Experts say the body begins losing oxygen minutes after an airplane leaves the ground. The air pressure in a plane during flight is lower than at sea level. This makes it more difficult for the body to effectively use the same amount of oxygen as it would on the ground. Fewer oxygen molecules （分子） cross the tissues (组织) in the lungs and reach the bloodstream.

　　The result is a five to twenty percent drop in the amount of oxygen in the blood. This reduces the amount of oxygen that reaches the organs of the body.

　　One effect of this lack of oxygen to the brain is a headache. When this happens, the heart attempts to fix the situation by beating harder and faster. This can make the traveler feel tired.

　　These signs of hypoxia are not dangerous in a healthy person. But a drop in oxygen level can cause a health emergency in people with heart or lung problems. They might lose consciousness or even suffer a heart attack.

　　Experts say that smoking cigarettes and drinking alcoholic liquids also reduce the body's ability to use oxygen. So they suggest that people not drink alcohol or smoke cigarettes either before or during a flight. They also say persons with heart or lung problems should seek advice from their doctors before flying.

1. The author writes the passage mainly to ___.

　　A. warn people in airplanes of possible dangers

　　B. offer some advice on avoiding health problems

　　C. explain the causes and effects of hypoxia

　　D. advise people not to smoke or drink alcohol

2. According to the passage, what leads to hypoxia?

　　A. The brain lacks enough oxygen.

　　B. The air pressure in a plane is too high

　　C. Our body needs less oxygen during takeoff.

　　D. The bloodstream contains no oxygen molecules.

3. The underlined part "fix the situation" means "___".

　　A. use more oxygen it needs B. increase the air pressure

　　C. reduce the amount of blood D. bump more blood to the brain

4. Why should passengers not smoke or drink before flying?

They weaken the body's ability to use oxygen.