医院感染发生的主要原因是什么？
参考答案：
个体抵抗力下降，免疫功能受损；侵人性诊疗机会增加；抗生素滥用；医院管理机制不完善。
--____does Kitty go to school?
--She takes a bus. [ ]
A. How
B. Why
C. When
D. Where
My mother asked me______ enter my room.
A．whether she could
B．when could she
C．that she can
D．how can she
