问题 选择题

一个细胞经过连续两次分裂,形成新细胞的数目是(  )

A.2个

B.4个

C.6个

D.8个

答案

细胞的分裂是指一个细胞分成两个细胞的过程,一个细胞经过一次分裂,形成两个新细胞.两次分裂后,形成四个新细胞.1个细胞分裂N次后的个数是2N.因此一个细胞十次裂后,可以形成新细胞的个数是210═1024(个).

故选B.

阅读理解

Each nation has many good people who help take care of others. For example, some high school and college students in the United States often spend many hours as volunteers in hospitals, orphanages(孤儿院) or homes for the aged(老人). They read books to the people in these places, or they just visit them or listen to their problems. Other young volunteers go and work in the homes of people who are sick or old. They paint, clean up, or repair houses, do shopping and mow(割草) their lawns(草坪). For boys who no longer have fathers, there is an organization called Big Brothers. College students and other men take these boys to basketball games or on fishing trips and help them get to know things that boys usually learn from their fathers.

Some cities have a number of clubs where boys and girls can go to play games or learn crafts(手艺). Some of these clubs show movies or organize short trips to the mountains, the beaches, museums or other places of interest. Most of these clubs use a lot of high school and college students as volunteers because they are young enough to remember the problems of younger boys and girls.

Volunteers believe that some of the happiest people in the world are those who help bring happiness to others.

根据短文内容,选择正确答案(10分)

小题1:From the short passage we can see that     are often helped by the volunteers.

A、workers in the factory  

B、students in school

C、people in the home for the elderly(老人)

小题2:Young volunteers often go and work in the homes when people are       .

A、very busy                B、hungry               C、in trouble

小题3:Big Brothers is an organization     .

A、to play basketball with the boys who no longer have fathers

B、to help the boys who no longer have fathers

C、to teach the boys who no longer have fathers how to fish

小题4:Which of the following don’t the clubs do for the boys and girls?

A、Show movies.

B、Organize short trips.

C、Make new clothes for them.

小题5:The clubs use many students as volunteers because      .

A、they believe that the happiest people are those who help bring happiness to others

B、they are so young that they can remember the problems of younger boys and girls

C、they can work very long a day without having a rest

判断题