问题 选择题

2010年“中国水周”的主题是“关注水质、抓住机遇、应对挑战”。我们应该了解水、爱护水资源。下列说法错误的是( )

A.为使水中的悬浮杂质沉降,可在水中加人适量的明矾

B.通过过滤的方法可以将不溶于水的固体杂质与水分离开来

C.铁可以和热水发生反应,并且可以生成氧化铁

D.5mL水和5mL酒精混合,溶液体积小于10mL,说明分子间有空隙

答案

答案:C

单项选择题
单项选择题

A

Ask Dr Jeffers.

This month Dr. Jeffers is answering questions about human brain and how it works. Dear Dr. Jeffers,

One of my colleagues, Felix Moeller, told me that scientists are learning to use computer to ’read minds’. Is there any truth to this story

--Jane Leon, New York, USA

Dear Ms. Leon,

Well, a lot of research is being conducted in this area, but so far, the brain scanning equipment and corresponding computer programs haven’ t been able to actually read thoughts. In one experiment, test subjects(受试者) were connected to scanning equipment and shown two numbers on a screen. They were then asked to choose between adding or subtracting(减)the two numbers. Using this method, researchers were able to follow brain processes and make the correct assumptions (假 设) 70 percent of the time. It’ s not quite mind reading, but it’ s certainly a first step.

--Dr. J.

Dear Dr. Jeffers,

My three-year-old son loves it when I dig my fingers into his sides and tickle (胳肢)him until he laughs uncontrollably. The other day I noticed him trying to tickle himself but he couldn’t do it. Why not

--Glenn Lewis, Vancouver, Canada

Dear Mr. Lewis,

It’s because of how the brain works. The brain is trained to know what to pay attention to and what to ignore. It causes us to ignore physical feelings we expect to happen, but it causes a mild panic reaction when there is an unexpected feeling. For example, you don’ t notice how your shoulder feels while you’ re walking down the street. But if someone comes up behind you and touches you lightly on the shoulder, you may jump in fear. It’ s that unexpected part that causes the tickle reaction.

--Dr. J.

People laugh when tickled by others because the feeling is().

A. unexpected

B. expected

C. comfortable

D. uncomfortable