问题描述：
_____ you return the book by Saturday,I will lend it to you.
A.Only if B.As long as C.So long as D.both B and C
我想问so long as不是只能用于否定句吗?为什么可以选C?
A.Only if B.As long as C.So long as D.both B and C
我想问so long as不是只能用于否定句吗?为什么可以选C?
问题解答：
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