问题描述:
一道英语语法题,求高手解答
Anyone,once ___ positive for H7N9 flu virus, will receive free medical treatment.
A. tested B.being tested
答案是A,请问为什么不选B,不是有个once吗?这边的once有什么用?
Anyone,once ___ positive for H7N9 flu virus, will receive free medical treatment.
A. tested B.being tested
答案是A,请问为什么不选B,不是有个once吗?这边的once有什么用?
问题解答:
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