| Since the Hawaiian Islands have never
been connected to other landmasses, the great variety of plants in Hawaii must
be a result of the long-distance dispersal of seeds, a process that requires
both a method of transport and an equivalence between the ecology of the source
area and that of the recipient area. There is some dispute about the method of transport involved. Some biologists argue that ocean and air currents are responsible for the transport of plant seeds to Hawaii. Yet the results of flotation experiments and the low temperatures of air currents cast doubt on these hypotheses. More probable is bird transport, either externally, by accidental attachment of the seeds to feathers, or internally, by the swallowing of fruit and subsequent excretion of the seeds. While it is likely that fewer varieties of plant seeds have reached Hawaii externally A. discussing different approaches biologists have taken to testing theories about the distribution of plants in Hawaii B. discussing different theories about the transport of plant seeds to Hawaii C. discussing the extent to which air currents are responsible for the dispersal of plant seeds to Hawaii D. resolving a dispute about the adaptability of’ plant seeds to bird transport [单项选择]Since we have never been here before, we do not know which bus（）
A. should we take B. to be taking C. to take D. should take [单项选择]（ ） for your help, we never have been able to overcome the difficulties.
A. Had it not B. lf it were not C. Had it not been D. If we had not been [单项选择]（） for your help, we’d never have been able to get over the difficulties.
A. Had it not B. If it were not C. Had it not been D. If we had not been [单项选择]（ ） for your help, we’d never have been able to get over the difficulties.
A. Had it not B. If it were not C. Had it not been D. If we had not been [单项选择]______for your help, we’’ d never have been able to get over the difficulties.
A. Had it not B. If it were not C. Had it not been D. If we had not been [单项选择]There seems never to have been a civilization without toys, but when and how they developed is unknown. They probably came about just to give children something to do.
In the ancient world, as is today, most boys played with some kinds of toys and most girls with another. In societies where social roles are rigidly determined, boys pattern their play after the activities of their fathers and girls after the tasks of their mothers.. This is true because boys and girls are being prepared, even in play, to step into the roles and responsibilities of the adult world. What is remarkable about the history of toys is not so much how they changed over the centuries but how much they have remained the same. The changes have been mostly in terms of craftsmanship, mechanics, and technology. In Egypt, the Americas, China, Japan and among the Arctic (北极的) peoples, generally the same kinds of toys appeared. Variations depended on lo- cal customs and ways of life because toys imitate(模仿) th A. You can’t find the similar kind of toy in all countries. B. The changes of toys have been mostly in terms of functions. C. The variations of toys depended on the thoughts of inventors. D. Available materials will put limit to each rattle. 我来回答: 提交
|
