开采易自燃煤层时，采煤工作面最好的通风方式是（）。
A、后退式
B、前进式
C、U型后退式
D、Y型后退式
参考答案：C
—Has he changed his mind?
—Yes. After some hours of discussion, I ____ to talk him into accepting the new plan.
A．had managed
B．would managed
C．have managed
D．managed
如果企业负债资金为零，则财务杠杆系数为1。 ( )
