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【单选题】
What does the word precursor in the context in the second paragraph mean? 查看材料A.
A man that may come before the happening of an earthquake.
B.
The leading factor that may cause a series of events to occur.
C.
Any meaningful sigh that indicates some would-be happenings.
D.
An event that may have symbolic or significant nature.
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【简答题】Of all the sports I do, I like swimming _____.
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