变频器的调速原理是通过改变输入信号的()来达到改变电动机的转速。
A、频率;
B、相位;
C、电压;
D、以上都要变化。
参考答案:D
急性肾衰竭少尿期的治疗原则不包括()
A.控制感染
B.调节电解质平衡
C.补液原则应"量出为入"
D.必要时采用透析治疗
E.采用低蛋白、低热量、高纤维素饮食
Near the church _____ cottage. [ ]
A. was such an old
B. had a so old
C. was such old a
D. is so an old