Hi ,
I am new to this forum , so may not be using the correct way to access my query sorry for this but curious to know the answer that's why posting it here .

Few Sentences' :

1.It is done
2.It was taught in the class
3.John,Who is believed to have gone
4.It was taken on the rocks

It seems that the above sentences are not correct , in each sentence past participle has been preceded by is/was
example: is done /was taught .Please tell me if the above sentences are correct or not .Reply would be highly appreciated .

thanks,
Deepak