They were heard ______ in the next room every night.A.talking B.to talk
问题描述：
They were heard ______ in the next room every night.
A.talking B.to talk
答
to talk
答
to talk 被动语态中省掉的to要加上，主动句为hear sb do sth ,变为被动句要将省掉的to加上
答
B to talk
根据题意：他们每天晚上都被听到在谈论.
原句：We heard them talk in the next room every night （ heard sb.do sth)
被动语态：They were heard to talk in the next room every night
heard sb.doing sth 是指在某一个时间点发生的事情.