问题描述：
把下列主动语态改为被动语态：when did they build the house?hav
把下列主动语态改为被动语态：
when did they build the house?
have they posted the letter yet?
we often see him help his classmate.
they will say nothing more about his matter.
把下列主动语态改为被动语态：
when did they build the house?
have they posted the letter yet?
we often see him help his classmate.
they will say nothing more about his matter.
问题解答：
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