Question Detail

they play cricket.

Cricket was played by them
Cricket are played by them.
Cricket is played by they.
Cricket is play by them.
Cricket is played by them.

Answer: Option E

1. Switch on the cooler.

Let cooler be switch on.
Switch on the cooler please.
Let cooler be switched on.
Let the cooler be switched on.

Answer: Option D

2. Sita was reading the Gita.

The Gita was being read by Sita.
The Gita were being read by Sita.
Gita was being read by Sita.
The Gita was read by Sita.

Answer: Option A

Explanation:

Note: Assume if we had "Someone was reading the Gita", then active voice would be,

The Gita was being read.

3. We must have obeyed our teachers.

Our teachers might have obeyed.
Our teachers might have been obeyed.
Our teachers must have been obeyed.
Our teachers must have obeyed.

Answer: Option C

Explanation:

If we have "Subject + Modal Auxiliary verb + have + third verb + object"
then we change it to

Passive subject + Modal Auxiliary verb + have been + third form + by + passive object.

Modal Auxiliary verb are : can, could, shall, will, may, might, should, would, must, ought to etc.