汽轮机按热力特性可以划分为( )汽轮机。
A．凝汽式
B．背压式
C．抽汽式
D．多压式
E．塔式
参考答案：A,B,C,D
______ many times, but he still couldn't understand it. [ ]
A. Having been told
B. Though had been told
C. He was told
D. Having told
血管紧张素转化酶抑制剂的主要适应证是（）、充血性心力衰竭。
