单选题

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 than internally, more varieties are known to be adapted to external than to internal transport.

单选题 The author of the passage is primarily concerned with ______.

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

【正确答案】 B

【答案解析】本文作者主要讨论各种有关把植物种子输送到夏威夷的理论。首先，生物学家们认为，由于海洋和气流的缘故，植物的种子被输送到夏威夷；其二，漂浮实验以及气流低温实验结果对有关假设提出质疑；其三，鸟类最有可能把种子带到夏威夷。

单选题 The author mentions the results of flotation experiments on plant seeds most probably in order to ______.

A、 support the claim that the distribution of plants in Hawaii is the result of the long distance dispersal of seeds
B、 lend credibility to the thesis that air currents provide a method of transport for plant seeds to Hawaii
C、 suggest that the long-distance dispersal of seeds is a process that requires long periods of time
D、 challenge the claim that ocean currents are responsible for the transport of plant seeds to Hawaii

【正确答案】 D

【答案解析】作者提到植物漂浮实验结果，很可能是为了质疑洋流致使植物的种子被输送到夏威夷这一观点。生物学家们认为，海洋和气流是植物的种子被输送到夏威夷的主要原因，但漂浮实验以及气流低温实验结果对上述观点提出了质疑。

单选题 It can be inferred from information in the passage that the existence in alpine regions of Hawaii of a plant species that also grows in the southwestern United States would justify which of the following conclusions?

A、 The ecology of the southwestern United States is similar in important respects to the ecology of alpine regions of Hawaii.
B、 There are ocean currents that flow from the southwestern United States to Hawaii.
C、 The plant species discovered in Hawaii must have traveled from the southwestern United States only very recently.
D、 The plant species discovered in Hawaii reached there by attaching to the feathers of birds migrating from the southwestern United States.

【正确答案】 A

【答案解析】在一些重要的方面，美国西南部的生态与夏威夷高山地区的生态大致相同。根据第一段，来源区(source area)和受援区(recipient area)的生态大致相同，两个地区就能长出同一种植物。在夏威夷的高山地区生长的植物也能在美国的西南部生长，这说明来源区和受援区的生态大致相同。

单选题 The passage supplies information for answering which of the following questions?

A、 Why does successful long-distance dispersal of plant seeds require equivalence between the ecology of the source area and that of the recipient area?
B、 Why are more varieties of plant seeds adapted to external rather than to internal bird transport?
C、 What varieties of plant seeds are birds that fly long distances most likely to swallow?
D、 What is a reason for accepting the long-distance dispersal of plant seeds as an explanation for the origin of Hawaii flora?