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  3. The plant called the scarlet gilia can have either red or white flowers. It had long been thought that hummingbirds, which forag

The plant called the scarlet gilia can have either red or white flowers. It had long been thought that hummingbirds, which forag

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问题 The plant called the scarlet gilia can have either red or white flowers. It had long been thought that hummingbirds, which forage by day, pollinate its red flowers and that hawk-moths, which forage at night, pollinate its white flowers. To try to show that this pattern of pollination by colors exists, scientists recently covered some scarlet gilia flowers only at night and others only by day: plants with red flowers covered at night became pollinated; plants with white flowers covered by day became pollinated. Which of the following, if true, would be additional evidence to suggest that hummingbirds are attracted to the red flowers and hawkmoths to the white flowers of the scarlet gilia?
选项 A、Uncovered scarlet gilia flowers, whether red or white, became pollinated at approximately equal rates.
B、Some red flowers of the scarlet gilia that remained uncovered at all times never became pollinated.
C、White flowers of the scarlet gilia that were covered at night became pollinated with greater frequency than white flowers of the scarlet gilia that were left uncovered.
D、Scarlet gilia plants with red flowers covered by day and scarlet gilia plants with white flowers covered at night remained unpollinated.
E、In late August, when most of the hummingbirds had migrated but hawkmoths were still plentiful, red scarlet gilia plants produced fruit more frequently than they had earlier in the season.
答案D
解析 本题的结论是：蜂鸟只在白天为红花授粉而天蛾只在夜间为白花授粉。(D)蜂鸟在白天觅食，白天被遮住的红色花朵未被授粉，从另一方面说明了红色花朵不会吸引在夜间觅食的天蛾，也就是说红花只吸引白天觅食的蜂鸟。同理，夜间被遮住的白色花朵未被授粉说明了白花只吸引夜间觅食的天蛾，由以上分析可知(D)正确；(A)与本题的结论无关；(B)说明红花不吸引蜂鸟和天蛾，反驳了结论；(C)引入了新的比较，因此(C)不对；(E)提出了与结论无关的新概念。
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