In the past several weeks, many cities in Northern China        from heavy fogs and severe cold.

A．had suffered

B．have been suffering

C．were suffered

D．suffered

依法应当进行消防设计审核的建筑工程的消防设计文件应由()报送公安机关消防机构审核。

A.建设单位

B.设计单位

C.施工单位

D.监理单位