主动语态变为被动语态例句：
一般现在时：
主：We believe him.
被：He is believed by us.
一般过去时：
主：He bought his children some pens.
被：Some pens were bought for his children by him.
一般将来时：
主：Everyone will know the truth soon .
被：The truth will be known by everyone.
现在进行时：
主：Mary is making a doll.
被：A doll is being made by Mary.
过去进行时：
主：They were carrying the hurt player.
被：The hurt player was being carried by them .
现在完成时：
主：He has received the letter.
被：The letter has been received by him.
过去完成时：
主：They had built ten bridges.
被：Ten bridges had been built by them
追答一般现在时/过去时
例：
1、主动：The children gave the foreign guests a warm welcome.
被动：The foreign guests were given a warm welcome by the children.
孩子们热烈地欢迎外宾。
2、
主动：People regard him as brilliant.
被动：He is regarded as brilliant by people.
人们认为他很有才华。
追问有从句吗？
追答从句里有被动是吗，那就改一下其中个句子就好了啊
I didn't know whether the letter had been received or not.
Everybody saw that the hurt player was carried by them.