—What's the matter with Philips?

—Something must have happened to him. He left home three hours ago, but ________ at the party!

A．didn't arrive

B．isn't arriving

C．hadn't arrived

D．hasn't arrived

可以作临时避难场所，当火场中人员生命受到烟气和热辐射的威胁时，可以暂时进入泡沫中，用（）来屏蔽烟和热的影响，以保存生命的。

A.高倍数泡沫

B.中倍数泡沫

C.低倍数泡沫

D.超倍数泡沫