在对投资方案进行经济效益评价时，单方案经济评价指标有( )。
A．NPV
B．Pt
C．NPVR
D．NAV
E．IRR
参考答案：A,B,D,E
—I must thank you for taking the trouble to look after my sick mother.
—_______.
A．With pleasure
B．It doesn’t matter
C．It was no trouble at all
D．By all means
气囊式蓄能器只能水平安装。（）
