The Passive voice

The passive
1 We form the passive with the verb be and the past participle.
2 Notice how the subject and object change in active and passive sentences.
The French invented tin cans.
Tin cans were invented by the French.
10.2
We call the subject the agent in passive sentences.
When we mention the agent, we use by.

The passive
1 We often use the passive when we don’t know who the agent is, when the agent is already obvious, or when the agent is not important for the action.
1 Millions of highly polluting cars are manufactured every year.
2 The criminals were arrested last night.
3 Several paintings were stolen last year. The police are still looking for the thieves.
10.2
We don’t know who stole the paintings.
Who makes the cars is not important.
We all know who arrests criminals.