Once _______, this power station will supply all the neighboring towns and villages with electricity. A. it being completed B. it completed C. completed D. it completes说明原因
问题描述：
Once _______, this power station will supply all the neighboring towns and villages with electricity.
A. it being completed B. it completed C. completed D. it completes
说明原因
答
C (being) completed的省略.