What is the first thing you want to do when you see someone yawn(打哈欠)? You want to yawn, too! Yawning is contagious.

    Scientists have found that all people yawn. Babies start to yawn even before they are born. The earliest yawn takes place when a baby is still inside its mother. When young children are about one year old, they start to yawn when they see others yawning. That's why scientists seem to think yawning is contagious.

    It's no secret that yawning is contagious, but why do we yawn? Well, scientists are not really sure.

    Some think we yawn because we feel bored. Recently scientists studied two groups of students between the ages of 17 and 19. One group watched music videos, and the other watched a boring color test. Scientists compared the numbers of their yawns and found that the color test group yawned more times than the video group.

    Another reason about yawning has to do with breathing. Some scientists believe that when we are bored or tired, we breathe more slowly. As our breathing slows down, we cannot get rid of(去除) enough carbon dioxide (CO₂) in our bodies. When there is too much carbon dioxide, our bodies will tell the brains (大脑) to breathe deeply. The result is a big yawn.                                                           

    In 2007, scientists suggested a new reason. They said that the reason people yawned was to cool down their brains. These scientists found that people who were warmer than others yawned more often.

    Scientists are still trying to find out why yawning happens and why it is so contagious. But they are only sure that when one person yawns, almost everyone else nearby wants to yawn, too.

____ 记述马可·波罗的东方经历和见闻，后来在欧洲广为流传，激起欧洲人对东方的憧憬和向往。

    We eat food with the help of hands every day. It is possible for some germs(细菌) to get into our bodies. So it is important to know how to wash hands in the right way.

    A piece of news from CCTV says that students from Guangzhou have a good way of learning how to wash hands. They learn it through doing hands-washing exercises during the ①break. The teachers there say most students wouldn't like to listen but they like to act. So now the students are interested in the interesting exercises. They are learning carefully. ②They want to be teachers for their parents and friends after they learn them well.

选出下面语句中与课文相同的一项（     ）

2014年5月在上海举行的“亚信”峰会期间，我国与俄罗斯签署了天然气供销合同。