Nowadays, children are ________ too many violent online games, which is bad for the development of their characters.

A．defeated by

B．limited to

C．handled by

D．exposed to

下面哪几个选项属于节约空调能耗的有效方法？（）

A、适当调高空调温度

B、缩短使用时间

C、关闭阀门

D、防止冷气外漏