问题 选择题

若要在同一视野中看到的细胞最多,宜选用的一组镜头是:   ( )                                                

答案

答案:C

题目分析:物镜是安装在转换器上的,有螺纹,目镜安放在镜筒上,没有螺纹,因此①②⑤是物镜,③④⑥是目镜;显微镜的放大倍数越大,视野就越小,看到的细胞就越大,但看到的数目较少,显微镜的放大倍数越小,视野就越大,看到的细胞就越小,但看到的数目细胞数目就越多,显微镜的放大倍数的计算是目镜的放大倍数乘以物镜的放大倍数,因而要想看到细胞的数目最多,显微镜的放大倍数应是最小,即最小目镜和物镜组合,物镜中放大倍数最小的是①,物镜中放大倍数最小的是③,所以若要在同一视野中看到的细胞最多,宜选用的一组镜头是①③。

点评:此题为基础题,解本题的关键是:一、显微镜目镜和物镜的区分方法,二、细胞数目与放大倍数的关系。

阅读理解

阅读与表达。

     Each year, a half-million people die from smoking in China which in 1990 overtook the United States

in the number of such deaths. And by the year 2025, 2 million Chinese will die each year from smoking

and related diseases, Professor Wang said when he talked about a report from the World Health

Organization.

     With westerners increasingly (日益)dropping the habit, the smoking population in China is on a

constant increase. "In 1964 the smoking population in America was 54 percent, which dropped to 26

percent by the year 1996," Wang said smoking has become a popular game, especially among young

people and women. Wang pointed out that women are more and more the targets (目标) of tobacco

selling. "As China sees repaid changes in women's role (角色), smoking among women is increasing,

with most new smokers being educated women."

     Wang said that in countries such as the United States and Britain where female smoking was popular

long ago, there were more lung cancers caused by smoking than breast cancers (乳腺癌), becoming the

largest cancer-killer of women.

     "At present only some 8 percent of Chinese women smoke, which has kept the total smoking

population below 40 percent. If women in China insist on demanding the same rights as men, the figure

will at least double in the present one." Wang said.

1. What does the underlined word "overtook" mean in the first paragraph?

    ____________________________________________________________________

2. Why is smoking among women increasing?

    ____________________________________________________________________

3. Why do more Americans give up smoking?

    ____________________________________________________________________

4. What's the main idea of the last paragraph?

    ____________________________________________________________________

单项选择题