Nobody but doctors or nurses and those __________ by Dr. Hu ________ to enter the patient's room.

A．invited；is allowed

B．are invited；are allowed

C．being invited；allowed

D．invited；are allowed

当吸程不够时，一般不采用（）来实现泵的运行正常。

A.增大吸入管径

B.减小吸入管径

C.缩短吸入管径

D.提高吸入口压差