31.My father will take me to Ho Chi Minh City next week. -
=> I will be taken to Ho Chi Minh City by my father next week
32.A man returned the keys to me.
=>  the keys were returned to me by a man 
33.Mary will see her friends off at the station.
=> Mary's friends will be seen  off at the station.
34.Workers were digging a large hole in the ground. 
=> a large hole was being dug in the ground by Workers