4 Complete the sentences with the correct passive form of the
verbs in brackets.
1 The prisoners are locked (lock) in their cells at 9 p. m. every night
2 John looked back. He thought he _ (follow).
3 Last time Tina went clubbing, her phone_ (steal).
4 Police are investigating the robbery but nobody_ arrest)
5 As I'm writing this, three suspects (question).
6 A press conference (hold) tomorrow.

Please refer to Explanation

Explanation:

Passive form is used when the subject is not the one to be emphasized but rather the action itself as well as the object. For example, instead of saying, " He stole my laptop", you say, "My laptop was stolen by him" if it is a Present Simple Tense. Using a Past Continuous Tense you would say, "My Laptop WAS BEING STOLEN by him" instead of, " He was stealing my laptop".

The corrective Passive forms for the following are,

2. John looked back. He thought he WAS BEING FOLLOWED.

3 Last time Tina went clubbing, her phone WAS STOLEN.

4 Police are investigating the robbery but nobody HAS BEEN ARRESTED.

5 As I'm writing this, three suspects ARE BEING QUESTIONED.

6 A press conference WILL BE HELD tomorrow.