泵机设备正常运转率为（），并一个月考核一次。
A.80%
B.100%
C.75%
D.95%
参考答案：D
AZDN着火时最好是用（）灭火，可控制AZDN分解。
A、CO2
B、水
C、干粉
D、泡沫
I _____ an exchange student here for a year now. [ ]
A. am
B. was
C. have been
D. had been
