根据短文理解，选择正确答案。

    Pollution inside homes and other buildings kills more than 4 million people each year. Many people die as a result of breathing smoke or from cooking over wood-powered or coal-powered stoves.

    One way to reduce the number of deaths is through cooking equipment powered by the sun. Crosby Menzies, a solar power expert in a South African company, described his latest solar cooker called the "Sol-4". "It is four square meters of mirrors, six to eight meters in length. It is quite a large cooker. "

    The "Sol-4" works by reflecting (反射) light from the sun off large mirrors. The mirrors direct (把……对准) the light at a cooking pan. Then the light heats the pan with solar energy. Within two minutes, the pan is hot enough to cook sausages and onions. In just four minutes, water can be boiled. That is as fast as cooking with natural gas or electricity.

    The cooker is also much "friendlier" than other models because people do not have to stand in the sun to use it. And people can prepare meals without having to collect firewood or spend money on coal. Such individuals would be less likely to have breathing illnesses from harmful smoke.

    At present, the cooker only works when the sun is shining. But engineers are working on a way to make it work without sunlight.

    Each cooker costs about $ 2,000, which is a large amount of money for most Africans. To solve that problem, Crosby Menzies has created a non-governmental organization called Solar Cookers for Africa.  It plans to raise money through donations to provide poor people with solar cooking equipment.

Have you ever experienced the feeling of falling as you start to fall asleep? Sometimes you may come to realize this feeling. If so, don't worry. Many people have felt the same thing.

In fact, these muscle twitches (肌肉抽搐) in the arms, legs or other parts of the body are called hypnic jerks (入睡抽动) or sleep starts. And they are very common. Up to 70 percent of people experience them sometimes, Huffington Post reported. But what causes it?

There are some theories(理论). Some scientists believe that the feeling of falling comes from the body relaxing itself, especially if the person is anxious or unable to get comfortable. As you're about to sleep, your muscles become relaxed. But your brain stays awake. It misunderstands the relaxing of your muscles as a sign that you're falling. Then the brain jerks the body awake as if it's trying to protect you.

    Other scientists believe that different phases of sleep might cause the hypnic jerks. When we sleep, we experience two phases: non-rapid eye movement (NREM) and rapid eye movement (REM). During REM, our heart rate (心率), breathing and nervous system can act irregularly (不规律地). If the body experiences flashes (一瞬间) of REM while entering sleep, these irregularities could cause twitches.

If you don't want to experience hypnic jerks, scientists have some suggestions. When you become deeply relaxed, you can learn how to reconnect slowly by moving your fingers and toes a little bit. Then start to move your head and open your eyes, while being aware of yourself as you get out of the relaxed state.

    But experts agree that hypnic jerks, though sometimes scary, are harmless. If it wakes you up, simply roll over and go back to sleep. But keep in mind: a caffeinated (含咖啡因的) drink, exciting evening activities or stress may make hypnic jerks happen more often.

阅读下列短文，从每题所给的四个选项（A、B、C和D）中选出最佳选项。

    Jogging is good for us and helps us live longer and healthier. It's easy to do and free. You do not have to spend money jogging. You can do it in a park or even in your home. But many people find it boring after jogging for a while. Then how can we keep jogging fun? Here are some ideas to make your jogging more interesting.

    First, you should choose to wear your favourite sports clothes and shoes when you jog. They make you more comfortable and more likely to run.

    Always jog outdoors. By changing your route, you can choose another street, and you will always have something interesting to enjoy when you jog.

Take along with your MP3 player and listen to your favourite songs when you jog. The music can make you excited and run farther without feeling bored.

    It's always more enjoyable with a friend. Make friends while jogging. Join a running club, find a new running partner, or invite an old friend to go jogging. It's better to find a friend who runs a little faster than you. Then you can try to catch up with him or her.

    As space science develops, man has learned more and more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger as well as success.

    Scientists have found out that the radiation（辐射）is the greatest danger to spacemen in space. When spacemen are working in space, they are in danger of the radiation from the sun and other stars, which is bad for their health. The harm of the radiation won't be found until their children even grandchildren are born. Some special medicine may work a little, but no really effective medicine has been found so far.

    Space rubbish is also thought to be a great danger to spacemen. It's reported that there were 9,000 man-made things flying in space. About 30% of these are satellites, 10% are spaceships, and the rest are space rubbish. An explosion（爆炸）in space in 1999 made a cloud of 300,000 fragments, each at least 4mm in size. A small piece of these even knocked a spaceship window and caused some damage（损坏）.

    Scientists are watching and reporting any possible danger all the time. They are working to deal with space rubbish. Although space is really dangerous, it interests many people on the earth. In the near future, it may be possible for people to spend a few days in a space hotel. We may even choose to leave the earth and live in space in a few years. So we should do something to help improve the space environment.