Since the Hawaiian Islands have never been connected to other land masses, 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 temperature 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. 【題組】46. The author of the passage is primarily concerned with _______.
(A) discussing different theories about the transport of plant seeds to
Hawaii
(B) discussing the extent to which air currents are responsible for the
dispersal of plant seeds to Hawaii
(C) resolving a dispute about the ability of birds to carry plant seeds
long distances
(D) resolving a dispute about the adaptability of plant seeds to bird
transport
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