下面各题中的两个量，（ ）成正比例．
A．一袋大米的重量一定，吃了的部分和剩下的部分
B．圆的面积和半径
C．圆柱体的体积一定，它的底面积和高
D．若3a=b，则a和b
A：吃了的重量+剩下的重量=这袋大米的总重量（一定），是和一定，所以吃了的与剩下的重量不成比例；
B：圆的面积÷半径=圆周率×半径（不一定），是比值不一定，圆的半径和面积不成正比例．
C：因为V=sh，圆柱体的体积一定，即圆柱体的底面积与高的乘积一定，所以圆柱体的体积一定，圆柱体的底面积与高成反比例；
D：因为3a=b，所以b：a=3（一定），是a、b的比值一定，所以a、b成正比例；
故选：D．
Directions: There are 10 blanks in the following passage. For each numbered blank, there are 4 choice marked A, B, C and D.
| During recent years we have heard much about "race": how this race does certain things and that race believes certain things and so on. Yet, the (51) phenomenon of race consists of few surface indications. We judge race usually from the coloring of the skin: a white race, a brown race, a yellow race and a black race. But (52) you were to remove the skin you could not tell anything about the race to which the individual belonged. There is nothing in physical structure, the brain or the internal organs to (53) a difference. There are four types of blood. All types are found in every race, and no type is distinct to any race. Human brains are the (54) No scientists could examine a brain and tell you the race to which the individual belonged. Brains will (55) in size, but this occurs within every race. (56) does size have anything to do with intelligence. The largest brain ever examined belonged to a person of weak (57) . On the other hand, some of our most distinguished people have had (58) brains. Mental tests which are reasonably (59) show no differences in intelligence between races. High and low test results both can be recorded by different members of any race. (60) equal educational advantages, there will be no difference in average standings, either on account of race or geographical location. |
A．remain
B．increase
C．decrease
D．vary