正弦电压相量<img src="https://nimg.ppkao.com/2018-08/yuanhao/2018083014375286672.jpg?sign=55537b7e73d3cd6bcb2fffb905373886&t=62d07239" />,频率为50HZ,则瞬时表达式为()。<br /> <img src="https://nimg.ppkao.com/2018-08/yuanhao/2018083014375635585.jpg?sign=1fe551edc72e48a84917a48e1fe5517b&t=62d07239" />
A、A
B、B
C、C
D、D