、在某对称星形连接的三相负载电路中，已知线电压 ，则 C 相电压有效值相量 ( ) 。

A、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/ueditor/jsp/upload/image/20161104/1478223703814052872_blob.png" title="12153103439724532" alt="blob.png"/>

B、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/ueditor/jsp/upload/image/20161104/1478223710155053941_blob.png" title="31359447786465666" alt="blob.png"/>

C、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/ueditor/jsp/upload/image/20161104/1478223716192023495_blob.png" title="9952017924605518" alt="blob.png"/>