Why do humans laugh? That question increasingly    1     (interest) scientists around the globe. People of all ages and cultures laugh spontaneously(不由自主地), and they spend quite a bit of time     2     (do) it. Laughter is a feature that we share    3     other great apes such as the chimpanzee and gorilla, which suggests that it is an ancient     4     (behave).

So this leads us to suggest that we are dealing here with a    5     (biology) adaptation, a character that gives humans some sort of evolutionary benefit. What could that be? There are different assumptions. One is that laughter signals social interest, especially in a romantic atmosphere. Not    6     (surprise), scientists find that a sense of humor is one of the most     7     (desire) characters in a partner.

Yet there are other reasons too    8     we laugh. For instance, laughter causes positive effect on people which will improve their abilities to learn new things. That’s why laughter and play go hand in hand. Especially for children, playful activities are an excellent way to learn new skills. And what laughter does    9     (be) to signal that they are in an environment     10     they are safe and they can play and learn.

【推荐2】Most students do an IQ test early in their school career. Even if they never see their results, they feel that their IQ is     1    determines how well they are going to do in life. When they see other     2    (student) doing better than them, they usually believe that those students have a     3    (high) IQ and that there is nothing they can do     4    (change) facts. However, new research into EQ suggests that success is not     5    (simple) the result of a high IQ.

While your IQ tells you how     6    (intelligence) you are, your EQ tells you how well you use your intelligence. Professor Salovery, who     7    (invent) the term EQ, gives the following description: At work, it is IQ     8    gets you promoted. Supported    9    his academic research, Professor Salovery suggests that when predicting someone’s future success, their character,     10    measured by EQ tests, might actually matter more than their IQ.

The skin is an essential part of your body and its largest organ. You have three layers of skin which act as a barrier against disease, poisons and the sun’s     1    (harm) rays. The functions of your skin are also very complex: it keeps you warm or cool; it prevents your body from     2    (lose) too much water; it is     3     you feel cold, heat or pain and it gives you your sense of touch. So as you can imagine, if you skin       4    (burn) it can be very serious. First aid is a very important first step in the       5    (treat) of burns.

The world itself is becoming much smaller because of the use of modern traffic and modern communication means. Life today is much easier than it     1    (be) hundreds of years ago. But it has brought new problems. One of the     2     (big) problems is pollution. Pollution comes in many     3     (form). We see it, smell it, drink it and we even hear it.

Man has been polluting the earth. The more people, the more pollution. Many years ago, the problem was not so serious     4    there were not so many people. When the land     5    (use) up or the river was dirty in     6     place, man moved to another place. But this is no longer true. Man is now     7    (slow) polluting the whole world.

Air pollution is still the most serious. It’s bad for all living things in the world. Water pollution     8    (kill) our fish and pollutes our drinking water. Noise pollution makes us become angry more easily. Many countries are making rules     9     (fight) pollution. They stop people from burning coal in houses and factories in the city, and putting dirty smoke     10     the air.

With the     1    (develop) of industry, air pollution is getting more and more serious. In Beijing, many people suffer different kinds of illnesses because    2     air pollution.

Air pollution is caused by the     3    (follow) reasons : about half of the problem is caused by vehicles. There are more and more cars, buses on the roads, and they   give off     4    (poison )   gases. 25% of air pollution is caused by factories. Another factor is the smokers. Smoking not only does harm to their health,     5     to others. Besides these, about 10% of air pollution is caused by other reasons.

We should take some    6     (measure) to fight against pollution. New fuel can be used to take     7     place of gas. We can plant     8     (many) trees than before.     9     everybody realizes the importance of environment and does something to stop pollution, the problem will     10    (solve).