美国GRE出国考试模拟试题13
Experiments show that insects can function as pollinators
of cycads, rare, palmlike tropical plants. Furthermore, cycads
removed from their native habitats—and therefore from
insects native to those habitats—are usually infertile. Nev-
(5) ertheless, anecdotal reports of wind pollination in cycads
cannot be ignored. The structure of cycads male cones is
quite consistent with the wind dispersal of pollen, clouds
of which are released from some of the larger cones. The
male cone of Cycas circinalis, for example, sheds almost
(10)100 cubic centimeters of pollen, most of which is probably
dispersed by wind. Still, many male cycad cones are com-
paratively small and thus produce far less pollen. Further-
more, the structure of most female cycad cones seems incon-
sistent with direct pollination by wind. Only in the Cycas
(15)genus are the females’ ovules accessible to airborne pollen,
since only in this genus are the ovules surrounded by a
loose ag美国GREgation of megasporophylls rather than by a tight
cone.
24.According to the passage, the size of a male cycad
cone directly influences which of the following?
(A) The arrangement of the male cone’s structural
elements
(B) The mechanism by which pollen is released from
the male cone.
(C) The de美国GREe to which the ovules of female cycads
are accessible to airborne pollen
(D) The male cone’s attractiveness to potential insect
pollinators
(E) The amount of pollen produced by the male cone
25. The passage suggests that which of the following is
true of the structure of cycad cones?
(A) The structure of cycad cones provides conclusive
evidence in favor of one particular explanation
of cycad pollination.
(B) The structure of cycad cones provides evidence
concerning what triggers the first step in the
pollination process.
(C) An irresolvable discrepancy exists between what
the structure of most male cycad cones suggests
about cycad pollination and what the structure of
most female cones suggests about that process.
(D) The structure of male cycad cones rules out a
possible mechanism for cycad pollination that is
suggested by the structure of most female cycad
cones.
(E) The structure of male cycad cones is consistent
with a certain means of cycad pollination, but
that means is inconsistent with the structure of英语作文
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