___the clouds, you would find the airplane in the sky easily

A．Had it not been for

B．If it were not

C．If it had not been for

D．Were it not for

在政府机构改革中，之所以坚持“不干事不能当干部”，是因为 

A．政府公职人员必须依法履行职责并承担法律责任

B．都干事才能提高政府的办事效率

C．政府职能是依靠政府公职人员来具体执行的　　

D．不干事有损于政府的形象