在操作过程中，动作的品质特征表现出一定的稳定性、精确性和灵活性，这属于操作技能形成的（）阶级。

A．操作定向

B．操作模仿

C．操作整合

D．操作熟练

Nobody but doctors, nurses or those ______ by Dr. Hu ______ to enter the patient's room.

A．invited; are allowed

B．are invited; are allowed

C．are invited; is allowed

D．invited; is allowed