项目评估的内部收益率（IRR）处于（）时，经济评估为正值。
A.IRR
B.IRR=O
C.IRR≈O
D.IRR>O
参考答案：D
If you keep working like this, your health will ________ under the pressure of work sooner or later. [ ]
A. break up
B. break down
C. break in
D. break out
感温式探测器能探测到火灾发生时产生的热量（热空气）信号，并把热量信号转化为（）电信号.
A.直流低压
B.直流高压
C.交流低压
