1. They often laughed at them
`->` They were often laughed by them.
2.They listened to our conversation very attentively
`->` Our converstation was listened very attentively.
3.I think they will wait for us only in a week
`->` I think we will be waited only in a week.
4.Nobody took notice of his late arrival
`->` His late arrival wasn't taken noitce.
5.We looked through all the advertisements very attentively
`->`All the advertisements were looked throught very attentively.
6.When ever he spoke the audience listened to him with great attention.
`->`Everything he spoken was listened to with great attention by the audience.