Jim didn’t come back untill 12 last night, so his father        very late waiting for him.

A．stayed up

B．stayed away

C．stayed over

D．stayed ahead

根据《空气质量飘尘中苯并[a]芘的测定乙酰化滤纸层析荧光分光光度法》（GB／T8971—1988），样品萃取时，将飘尘样品小心放进索氏提取器的渗滤管中，加入50m1环己烷置于温度为99±1℃水浴中（水面以达到接受瓶高的2／3为宜）连续回流（）上。

A.6

B.8

C.7

D.5