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.

    A recently study found people's lives are made shorter in North China. It is showed the life expectancy(平均寿命) had been cut down by 5.5 years there. Researchers think that the heavy air pollution in China should be to blame. It's really the truth. Our government has already done something. However, it doesn't seem to work so well.

    “Air pollution in China is doing harm to people's health. The harm is much more serious than we can imagine,” said Chen Yuyu of Beijing University, one of researchers of this study.

    Dirty air brings serious problems in North China. In January this year, the air pollution was worse than that in other places. That was caused by rising temperature and waste gas from coal heating.

    Chinese government should strongly fight against air pollution. They should think of more proper ways to deal with the problem. People should be encouraged to take buses, ride bicycles or walk, instead of driving cars. The factories that pollute heavily should be closed.

    “We need to improve our environment, although it might be expensive. Protecting our environment means protecting ourselves,” Li Hongbin, another researcher of the study said.

    April 22 is Earth Day. Everyone on Earth should care about and protect the earth!

    The earth has warmed by about 1°F (华氏度) over the past 100 years, but why and how? Well, scientists are not quite sure. Maybe the earth gets warmer and warmer on its own. But many scientists say that people are doing many things which makes the earth warmer. First, greenhouse effect (温室效应) is a very important reason for the change of the earth. People give out too much energy into the air every year. It makes the earth warmer. Climate (气候) change is another important reason. Sometimes it becomes too hot and sometimes too cold. Sometimes there is too much rain and sometimes too little. The change of the climate makes the earth warmer. In turn, the warmth of the earth changes the climate, too.

    When the earth becomes warmer, there may be more rain and a rise in sea level. It will affect the growth of plants, animals and people. On a Pacific island, 100 people have to move to higher ground because the sea is rising. These people can no longer live on the coast. Before that, two islands without people went underwater in 1999. Scientists say that the seas can rise by nearly one meter by 2100.

    People can affect the earth's air, land and water. As for us, we can do many things to protect the earth. For example, we can use fridges less. We can tell more people about protecting the earth.

    A thirsty crow(乌鸦) comes across(偶然遇到) a bottle of water, but the water level is out of its reach. The bird then drops some stones into it and gets the water.

    "It's just a story," you may think. But new research has found that crows' brains may sometimes be better than those of 6­year­old children.

In a recent experiment, American scientist Corina Logan and her team caught six crows to test them. The crows and children had to choose between two sets of tubes(试管). They had to drop stones in and get water.

    With the red set, when they dropped a stone into a wide tube, the water level raised in a connected narrow tube. The blue set of tubes, however, had no connection between them.

    Children aged 7 to 10 were able to learn the rule. Children aged 4 to 6, however, failed. Five of the six crows failed the test. But Kitty, a 6­month­old crow, passed it. She put most of the stones into the red tubes.

    So, could a bird be more clever than a kindergartner? Don't be too quick to say no.