、额定电压为 220V 的照明负载接于线电压为 380V 的三相四线制电源时，必须接 成 ( ) 形。

A、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/ueditor/jsp/upload/image/20161104/1478223443841073639_blob.png" title="4775336675103034" alt="blob.png"/>

B、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/ueditor/jsp/upload/image/20161104/1478223451226076590_blob.png" title="55910504927189995" alt="blob.png"/>

C、<img src="https://s3.cn-north-1.amazonaws.com.cn/qingshuxuetang/ueditor/jsp/upload/image/20161104/1478223460157036552_blob.png" title="5406662247907288" alt="blob.png"/>