they often see the boy help the blind man改为同义句The boy --- often --- --- ----- the blind man

题目

they often see the boy help the blind man改为同义句The boy --- often --- --- ----- the blind man

答案

The boy is often seen to help the blind man
see 是个感官动词,用在主动语态中用法是see sb do sth
用在被动语态中 to 要还原,变为 be seen to do sth