Once the pollen has been snatched by the wind, the fate of the pollen is obviously up to the vagaries of the wind, but not every

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问题     Once the pollen has been snatched by the wind, the fate of the pollen is obviously up to the vagaries of the wind, but not everything is left to chance. [A] Wind-borne pollen is dry, rounded, smooth, and generally smaller than that of insect-pollinated plants. [B] Small grains may be blown farther but they are also more prone to be whisked past the waiting stigma because smaller particles tend to stay-trapped in the fast-moving air that flows around the stigma. [C] But stigmas create turbulence, which slows the air speed around them and may help pollen stick to them. [D]
    Look at the four squares [■] that indicate where the following sentence could be added to the passage. But size is a two-edged sword.
    Where would the sentence best fit?

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答案B

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