、某三相电路中 A ， B ， C 三相的有功功率分别为 P A ， P B ， P C ，则该三相电路总有功功率 P 为 ( ) 。

A、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/ueditor/jsp/upload/image/20161102/1478064607205026339_blob.png" title="23008160791017417" alt="blob.png"/>

B、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/ueditor/jsp/upload/image/20161102/1478064617632085034_blob.png" title="14482082264967244" alt="blob.png"/>

C、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/ueditor/jsp/upload/image/20161102/1478064623737088875_blob.png" title="3221930816084906" alt="blob.png"/>