求助:一道大全的阅读

Species interdependence in nature confers many benefits on the species involved, but it can also become a point of weakness when one species involved in the relationship is affected by a catastrophe. Thus, flowering plant species dependent on insect pollination, as opposed to self-pollination or wind pollination, could be endangered when the population of insect-pollinators is depleted by the use of pesticides.

In the forests of New Brunswick, for example, various pesticides have been sprayed in the past 25 years in efforts to control the spruce budworm, an economically significant pest. Scientists have now investigated the effects of the spraying of Matacil, one of the anti-budworm agents that is least toxic to insect-pollinators. They studied Matacil’s effects on insect mortality in a wide variety of wild insect species and on plant fecundity, expressed as the percentage of the total flowers on an individual plant that actually developed fruit and bore seeds. They found that the most pronounced mortality after the spraying of Matacil occurred among the smaller bees and one family of flies, insects that were all important pollinators of numerous species of plants growing beneath the tree canopy of forests. The fecundity of plants in one common indigenous species, the red-osier dogwood, was significantly reduced in the sprayed areas as compared to that of plants in control plots where Matacil was not sprayed. This species is highly dependent on the insect-pollinators most vulnerable to Matacil. The creeping dogwood, a species similar to the red-osier dogwood, but which is pollinated by large bees, such as bumblebees, showed no significant decline in fecundity. Since large bees are not affected by the spraying of Matacil, these results add weight to the argument that spraying where the pollinators are sensitive to the pesticide used decreases plant fecundity.

The question of whether the decrease in plant fecundity caused by the spraying of pesticides actually causes a decline in the overall population of flowering plant species still remains unanswered. Plant species dependent solely on seeds for survival or dispersal are obviously more vulnerable to any decrease in plant fecundity that occurs, whatever its cause. If, on the other hand, vegetative growth and dispersal (by means of shoots or runners) are available as alternative reproductive strategies for a species, then decreases in plant fecundity may be of little consequence. The fecundity effects described here are likely to have the most profound impact on plant species with all four of the following characteristics: a short life span, a narrow geographic range, an incapacity for vegetative propagation, and a dependence on a small number of insect-pollinator species. Perhaps we should give special attention to the conservation of such plant species since they lack key factors in their defenses against the environmental disruption caused by pesticide use.

5.    It can be inferred that which of the following is true of plant fecundity as it is defined in the passage?

(A) A plant’s fecundity decreases as the percentage of unpollinated flowers on the plant increases.

(B) A plant’s fecundity decreases as the number of flowers produced by the plant decreases.

(C) A plant’s fecundity increases as the number of flowers produced by the plant increases.

(D) A plant’s fecundity is usually low if the plant relies on a small number of insect species for pollination.（A）

(E) A plant’s fecundity is high if the plant can reproduce quickly by means of vegetative growth as well as by the production of seeds.

这个题以前好象有讨论过,不过我还是不明白.

我觉得文章第二段是在讲fecundity 对population的影响啊，怎么会是第一个呢？第一个答案是反过来讲其他因素fecundity的引响啊．．．我选的第二个．恳请大家帮忙解惑，快要考试了．．．

我又看了一遍,的确是在讲fecundity产生的影响．．．但是按照常规的确应该是向a答案讲的那样来阐述，但是文章中我看不出来．．．

完了，我绕进去了．．．help...