By-agent - passive voice

Passive sentences: Fill in the by-agent.

The teacher opens the door. (Active)
The door is opened .  (Passive)
Mrs Tompson builds a house. (Active)
A house is build . (Passive)
The dog bites Amy. (Active)
Amy is bitten . (Passive)
John cooks a meal. (Active)
A meal is cooked . (Passive)
The rats sing a song. (Active)
A song is sung . (Passive)
The mechanic repairs the car. (Active)
The car is repaired . (Passive)
Tourists visit London every year. (Active)
Every year London is visited . (Passive)
The child eats cakes. (Active)
Cakes are eaten . (Passive)