最容易引起再生障碍性贫血的药物是
A．氯霉素B．磺胺嘧啶C．环磷酰胺D．保泰松E．他巴唑
参考答案：A
供热管道的地沟沟底应做不小于( )的坡度。
A．0.001B．0.002C．0.003D．0.004
Before starting to hoist provisions，which should be checked?（）
A.Hoist rope is not kinked
B.Multiple part lines are not twisted around each other
C.The hook is centrally located over the load
D.All of the above
