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题库 / OG2021-SC-857
Upon their first encountering leaf-cutting ants in South America, the insects seemed to some Europeans to be carrying bits of greenery to shade themselves from the tropical sun--hence the sobriquet "parasol ants.”
Upon their first encountering leaf-cutting ants in South America, the insects seemed to some Europeans to be
Upon their first encountering leaf-cutting ants in South America, some Europeans thought they were
On first encountering leaf-cutting ants in South America, it seemed to some Europeans that the insects were
On first encountering leaf-cutting ants in South America, some Europeans thought the insects were
On their first encounter with leaf-cutting ants in South America, some Europeans thought it was because the insects were
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考察知识点：
（1） first as adj. vs. adv。adj时，表示”第一的“”第一个的“，一般都要加the, my/his/her/their etc进行限定；adv时，表示”第一次“，不需要限定。
（2）前半句用的是encountering，后半句的主语应该是人，满足一致性原则
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