A strange man was watching us.
We were being watched by a strange man.
They could not have made the mistake.
The mistake could not have been made by them.
My absence was approved by my boss.
My boss approved my abscence.
They might make a donation.
A donation might be made (by them).
That email has to be sent by us, not them.
We have to send that email, not them.
He should improve his handwriting.
His handwriting should be improved.
Someone should have set the alarm.
The alarm should have been set (by someone).
Someone could have informed her about the issue.
She could have been informed about the issue (by someone).
Someone must have given her the correct answers.
She must have been given the correct answers.
