问题描述：
yet什么情况下用一般时态,什么情况下用完成时态,如何区分
When and where to build the new factory ____yet
a,is not decided b has not decided
为什么选B不选A
When and where to build the new factory ____yet
a,is not decided b has not decided
为什么选B不选A
问题解答：
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