问题 填空题

荷叶上两个小露珠靠近时能自动结合成较大的一滴,该现象说明了______.清晨草叶上常挂有晶莹的露珠,这是由于夜间温度低,空气中的水蒸气______形成的,在阳光照射下这些露珠又会慢慢消失,是由于露珠发生了______的缘故.雨后天空出现的彩虹是光的______现象.

答案

分子间都是存在着引力和斥力,荷叶上两个小露珠靠近时能自动结合成较大的一滴,说明分子间有相互作用的引力;

清晨草叶上常挂有晶莹的露珠是空中水蒸气变为液态的水而形成的现象,是液化现象;露珠又会慢慢消失是液态的水又变为了气态,液态变为气态的现象叫汽化.

雨后天空出现的彩虹,这是由于太阳光照到空气中的小水滴上,被分解为绚丽的七色光,即光的色散现象.

故答案:分子间有相互作用的引力;液化;汽化;色散.

单项选择题

Our ape-men forefathers had no obvious natural weapons in the struggle for (1) in the open. They had neither the powerful teeth nor the p claws of the big cats. They could not (2) with the bear, whose strength, speed and claws (3) an impressive " small fire" weaponry. They could not even defend themselves (4) running swiftly like the horses, zebras or small animals. If the ape-men had attempted to compete on those terms in the open, they would have been (5) to failure and extinction. But they were (6) with enormous concealed advantages of a kind not possessed by any of their competitors.

In the search (7) the pickings of the forest, the ape-men had (8) efficient stereoscopic vision and a sense of color that the animals of the grasslands did not (9) . The ability to see clearly at close range permitted the ape-men to study practical problems in a way that lay far (10) the reach of the original inhabitants of the grassland. Good long-distance sight was (11) another matter. Lack of long-distance vision had not been a problem for forest-dwelling apes and monkeys because the (12) the viewpoint, the greater the range of sight-so (13) they had had to do was climb a tree. Out in the open, however, this simple solution was not (14) . Climbing a hill would have helped, but in many places the ground was flat. The ape-men (15) the only possible solution. They reared up as high as possible on their hind limbs and began to walk (16) . This vital change of physical position brought about considerable disadvantages. It was extremely unstable and it meant that the already slow ape-men became (17) still. (18) , they persevered and their bone structure gradually became (19) to the new, unstable position that (20) them the name Homo erectus, upright man.

2()

A.match

B.compare

C.rival

D.equal

单项选择题