已知移动通信基站的高频开关电源系统中，安装3个50A整流器，这些整流器是（）关系。
A、并联
B、串联
C、混联
D、相互独立
参考答案：A
— Was the driving pleasant when you went to Mexico last summer?
— No, it ＿＿ for four days when we arrived, so the roads were very muddy.
A．was raining
B．had been raining
C．would be raining
D．rained
什么是新体诗？新体诗有哪些代表作家？
