密目网检查发现断裂或破洞应及时进行（）。
A、修理和更换
B、修理
C、更换
参考答案：A
The radio club often plays songs _______by students and gives messages to keep parents ____ of the latest news.
A．sung, exchanged
B．sang, broadcasted
C．singing, approved
D．sung, informed
试简述锅内水处理的防垢对策？
