螺杆式制冷压缩机停机时，关闭供液阀后将能量调节滑阀调节至（）。
A.50%
B.30%
C.25%
D.零位
参考答案：D
If you want to learn English well, you need __ it as much as possible. [ ]
A. practice speaking
B. to practice speaking.
C. to practice to speak
D. practicing speaking
有关厂界噪声测量的说法正确的有( )。
A．测量时段要选择在生产正常阶段和无雨无雪的天气B．读数不受外界环境的干扰C．大风天气应继续测量 D．一般采用同心圆布点法
