I ()TV whenmy mother () A.watched,came back B.was watching,came back C.was watching,was caming back

问题描述:

I ()TV whenmy mother () A.watched,came back B.was watching,came back C.was watching,was caming back

B
固定句式:sb.was doing sth when sth happened.
或:sth happened when sb was doing sth.
表过去某个正在进行的动作被中断