问题 填空题

判一判(填成正比例、反比例、或不成比例)

1.一个非零的自然数和它的倒数______.

2.一个人的年龄和它的体重______.

3.正方形的周长和它的边长______.

4.平行四边形的高一定,它的面积和底______.

5.看一本漫画书,平均每天看的页数和需要的天数.______.

6.报纸的单价一定,订阅的份数和总价.______.

7.运动员跳远的距离和他的身高.______.

8.在教室的地面铺方砖,教室的面积和需要的方砖的块数.______.

9.在一定的时间内,工人织布的总米数和每小时织布的米数.______.

10.圆的周长和它的直径.______.

答案

1、一个非零自然数×它的倒数=1(一定),是乘积一定,所以一个非零自然数和它的倒数成反比例;

2、一个人年龄和体重虽然是相关联的两个量,但是它们的比值和乘积都不一定,故不成比例;

3、正方形的周长÷边长=4(一定),是比值一定,所以正方形的周长和它的边长成正比例;

4、平行四边形的面积÷底=高(一定),是比值一定,所以平行四边形的高一定,它的底和面积成正比例;

5、每天看到页数×看的天数=一本书的总页数(一定),是乘积一定,所以每天看的页数和需要看的天数成反比例;

6、总价:订阅份数=的单价(一定),也就是总价与订阅份数的比值一定,所以订阅份数与总价成正比例;

7、因为跳远成绩与身高不是相关联的量,即比值和乘积是不一定的,所以跳远成绩与身高不成比例;

8、教室的面积÷需要的块数=每块方砖的面积(一定),所以教室的面积和需要的方砖的块数成正比例;

9、织布总米数÷每小时织布米数=所需时间(一定),是对应的比值一定,所以工人织布的总米数和每小时织布的米数成正比例;

10、圆的周长÷直径=π(一定),是比值一定,圆的直径和周长成正比例;

故答案为:成反比例,不成比例,成正比例,成正比例,成反比例,成正比例,不成比例,成正比例,不成比例,成正比例,成正比例,成正比例.

单项选择题

There have been several claims to have cloned humans over the past few years. Most have been bogus. But the announcement made this week by Woo Suk Hwang, of Seoul National University in South Korea, and his colleagues, is serious. It is the first to achieve the accolade of publication in a peer-reviewed scientific journal. Dr. Hwang s work appears in Science.

The terminology of human development has become slippery over the past few years, in the hands of both "life-begins-at-conception" propagandists who want to stop this sort of research, and publicity-seeking scientists who have claimed more than they have really achieved. What Dr. Hwang and his team have created is not what developmental biologists would normally refer to as an embryo. But it is a genuine scientific advance. South Korea’s researchers have taken egg cells from volunteer women, removed the nuclei from those cells (which contain only half of the genetic complement required to make a human being, since the other half is provided by the sperm), and replaced each nucleus with one taken from one of the volunteer’s body cells (which contains a full genetic complement). Given a suitable chemical kick-start, such re-nucleated cells will begin dividing as though they were eggs that had been fertilised in the more traditional manner. Since they have all of the mother’s genes, they count as clones.

Then the team cultured the dividing eggs until they had formed structures called blastocysts, with a few dozen cells each. This is the significant advance. At this stage the structure, though still just a featureless ball of cells, has started to differentiate into the body’s three basic cell types (known as endoderm, mesoderm and ectoderm). The researchers were able to extract cells from some of their blastocysts, and grow tissues containing all three cell types.

These are so-called stem cells, which can be directed to form a wide variety of the specialised cells from which organs are built. That, not the creation of new human beings, is the stated reason for this sort of research, since specialised cells made this way might be used to replace the cells lost in diseases such as Parkinson’s and type-Ⅰ diabetes. This process is known as therapeutic cloning.

No doubt Dr Hwang’s scientific success will sharpen the debate between those who see therapeutic cloning as a potential force for good, and those who see it as a step on the road to a cloned human being. The former have been queuing up to praise the scientist’s work. It is "a major medical milestone" that could help spur a "revolution", said Robert Lanza, a cloning expert.

But opponents of therapeutic cloning should not worry too much yet. The road from a blastocyst to a baby is a long and complex one. Nevertheless, the South Korean breakthrough makes it more urgent than ever that legislation be passed differentiating clearly between therapeutic and reproductive cloning—permitting the former and prohibiting the latter.

What does the word "bogus" (Line 2) most probably mean().

A. Different.

B. Fake.

C. Bold.

D. Genuine.

单项选择题