《煤矿安全规定》规定，采掘工作面应实行（）通风。
A、串联
B、分区
C、扩散
参考答案：B
I tried to persuade him to give up the foolish idea, but in ________, and now he begins to regret.
A．vain
B．turn
C．return
D．case
天车广泛采用补偿联轴器的种类有哪些？
