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原文：
Species interdependence in nature confers many benefits onthe species involved, but it can also become a point of weaknesswhen one species involved in the relationship is affected by acatastrophe. Thus, flowering plant species dependent on insectpollination, as opposed to self-pollination or wind pollination, couldbe endangered when the population of insect-pollinators isdepleted by the use of pesticides.
In the forests of New Brunswick, for example, variouspesticides have been sprayed in the past 25 years in efforts tocontrol the spruce budworm, an economically significant pest.Scientists have now investigated the effects of the spraying ofMatacil, one of the anti-budworm agents that is least toxic toinsect-pollinators. They studied Matacil’s effects on insect mortalityin a wide variety of wild insect species and on plant fecundity,expressed as the percentage of the total flowers on an individualplant that actually developed fruit and bore seeds. They found thatthe most pronounced mortality after the spraying of Mataciloccurred among the smaller bees and one family of flies, insectsthat were all important pollinators of numerous species of plantsgrowing beneath the tree canopy of forests. The fecundity of plantsin one common indigenous species, the red-osier dogwood, wassignificantly reduced in the sprayed areas as compared to that ofplants in control plots where Matacil was not sprayed. This speciesis highly dependent on the insect-pollinators most vulnerable toMatacil. The creeping dogwood, a species similar to the red-osierdogwood, but which is pollinated by large bees, such asbumblebees, showed no significant decline in fecundity. Sincelarge bees are not affected by the spraying of Matacil, these resultsadd weight to the argument that spraying where the pollinators aresensitive to the pesticide used decreases plant fecundity.
The question of whether the decrease in plant fecunditycaused by the spraying of pesticides actually causes a decline in theoverall population of flowering plant species still remainsunanswered. Plant species dependent solely on seeds for survivalor dispersal are obviously more vulnerable to any decrease in plantfecundity 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. Thefecundity effects described here are likely to have the mostprofound impact on plant species with all four of the followingcharacteristics: a short life span, a narrow geographic range, anincapacity for vegetative propagation, and a dependence on asmall number of insect-pollinator species. Perhaps we should givespecial attention to the conservation of such plant species sincethey lack key factors in their defenses against the environmentaldisruption caused by pesticide use.
7. Which of the following assumptions most probably underlies theauthor’s tentative recommendation in lines 45-48?（标黄处）
(A) Human activities that result in environmental disruption should beabandoned.
(B) The use of pesticides is likely to continue into the future.
(C) It is economically beneficial to preserve endangered plant species.
(D) Preventing the endangerment of a species is less costly than tryingto save an already endangered one.
(E) Conservation efforts aimed at preserving a few well-chosen speciesare more cost-effective than are broader-based efforts to improvethe environment.
不理解为什么OA是B，我选了A
求赐教！！
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发表于 2013-12-27 15:55:25
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