someone saw a stranger walk into the building,改为被动句

问题描述:

someone saw a stranger walk into the building,改为被动句

A stranger was seen by someone to walk into the building .
加油!不明白再问!句型结构是什么?固定用法:see sb do sth变被动结构时TO 要还原,即: sb be seen to do sth 根据SAW 可知是一般过去时,故BE 要用WAS(主语a stranger 是三单) ,SEE的过去分词是 seen