1) Kate is writing an essay right now. - An essay is being written by Kate right now.
2) The gangsters killed him yesterday morning. - He was killed by the gangsters yesterday morning.
3) I water the flowers every day. - The flowers are watered (by me) every day.
4) A postman has delivered an insured letter. - An insured letter has been delivered (by a postman).
5) I shall remember this story forever. - This story will be remembered (by me) forever.