为比较两所等级和规模均相同的医院的治愈率，若各医院各科病人数的内部构成不同时，为避免产生假象，关键要进行的是（）

A.分科比较

B.分病比较

C.率的标准化

D.率的参数估计

E.率的假设检验

In a crossing situation on open waters, a sailing vessel shall keep out of the way of all the following vessels except a vessel（）.

A.not under command

B.restricted in her ability to maneuver

C.engaged in towing

D.fishing