题目内容：

how long have there been mice in your attic?
—————————————————————————————— two months.
用for或since回答

优质解答

【There have been mince in my attic for】 two months
我的阁楼上有老鼠已经有两个月了.
for two months 这是现在完成时的时间状语.

追问：

为什么用there have呢

追答：

因为问句是 have there been，答句要改成陈述语序，也就是there have been。 there have been 是 there be的现在完成时态。