----- The windows must have taken you quite a long time that day.

----- Right. They ______ for months.

A．haven’t been cleaned

B．didn’t clean

C．hadn’t been cleaned

D．haven’t cleaned

开采可能波及水淹区域下的废弃防隔水煤柱时，应（），确保无溃水、溃浆（沙）威胁。

A.疏干上部积水

B.边探水边开采

C.进行安全性论证

D.报告主要负责人