在启动螺杆式压缩机前，若环境温度低于（）度时可暂时不向冷凝器、油冷却器供水，以使油温排气温度上升。
A.10
B.20
C.30
D.40
参考答案：C
—I saw Lucy go to Miss Zhang's home just now.
—Yes, she is often seen Miss Zhang with her housework. [ ]
A. help
B. to help
C. helping
热继电器整定值一般为被保护电动机额定电流的（）倍。
A、1.0
B、1.2
C、1.5
D、2.0
