求助者说，她儿子睡熟时突然起床，开门出外，两眼迷茫，过会儿回来又上床睡。次日问他昨夜出去做什么，他一点不知。这是（）

A.夜惊

B.梦魇

C.睡行症

D.发作性睡眠

E.嗜睡症

The police have started an ___ into the cause of the fire which broke out in the hotel last night.

A．appreciation

B．investigation

C．operation

D．extension