Active and Passive Voice

Which of the following sentences can be correctly transformed into the passive voice without changing the tense?

Choose the most appropriate passive form for the given sentences from the options:
A very old friend helped me.

Choose the most suitable passive voice conversion of the given sentence:
Nobody can predict future.

Choose the most appropriate option to fill in the blank:
Why ______ (Bill/sack) from his job? What did he do wrong?

Choose the correct passive form from the options given below:
A cardigan _ by the old lady at that time.

Frame a sentence in passive voice from the given information:
My car has disappeared. (it / steal!)

Change the following sentence to passive form.
Dust and smoke cause smog.

Rewrite the following in passive voice, without using 'somebody/they/people' etc.:
Somebody accused me of stealing money.

Change the following statement into passive voice:
The peon refused him admittance.

Choose the correct passive form of past tense from the options given below:
The flag __ by the Chief Guest.

The sentence has been given in the Active/Passive voice. From the given options, choose the one which best expresses the given sentence in the Passive/Active voice.
They had cleared the dues.

Choose the correct passive form from the options given below:
A cardigan by the old lady at that time.

Choose the correct passive form from the options given below:
English __ all over the world.

Change the following sentences into passive voice:
Do it.

Change the voice of the given sentence:
How much will they pay you?

Choose the correct passive form from the options given below:
A prayer _ by the choir in the church next week.

Rewrite the following sentence by changing its voice (Active or Passive):
The clown was being laughed at by them.

Choose the most appropriate passive form for the given sentences from the option:
The porter was carrying the luggage.

Choose the correct passive form from the options given below:
The letter __ by Rumi yet.

Choose the most suitable passive voice conversion of the given sentence.
The Principal will present vote of thanks before the dinner is served.