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  3. [A] Since wind-pollinated flowers have no need to attract insects or other a

[A] Since wind-pollinated flowers have no need to attract insects or other a

游客2024-01-02  31
问题     [A] Since wind-pollinated flowers have no need to attract insects or other animals, they have dispensed with bright petals, nectar, and scent. [B] The result is insignificant-looking flowers and catkins (dense cylindrical clusters of small, petal less flowers). [C] Wind pollination does, of course, require a lot of pollen. [D] Birch and hazel trees can produce 5.5 and 4 million grains per catkin, respectively. There are various adaptations to help as much of the pollen go as far as possible. Most deciduous wind-pollinated trees (which shed their leaves every fall) produce their pollen in the spring while the branches are bare of leaves to reduce the surrounding surfaces that "compete" with the stigmas (the part of the flower that receives the pollen) for pollen. Evergreen conifers, which do not shed their leaves, have less to gain from spring flowering, and, indeed, some flower in the autumn or winter.
    Look at the four squares [■] that indicate where the following sentence could be added to the passage. These are at best a waste and at worst an impediment to the transfer of pollen in the air.
    Where would the sentence best fit?
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答案 B
解析
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