根据现行《火灾自动报警系统设计规范》,当发生火灾时,疏散通道上的防火卷帘门应分()次落下
A.1
B.2
C.3
D.4
参考答案:B
We found _____ impossible to finish the work in such a short time.[ ]
A. it's
B. that was
C. it
D. that
专门委员会的工作性质及人员设置?