TV will have been bought by him by this time.

Green mangoes are sour when they are tested.

Let a pen be given to me.

Let not the poor be hated.

Was I seen by you before?

I was obliged to go.

The sentence "Whom did you see on the road?" is in the active voice.

Passive voice:
Who was seen by you on the road?

Explanation:
"Whom" becomes "Who" in the passive voice when it becomes the subject.

The verb "did see" (past simple) changes to "was seen" in the passive voice.

The sentence "The lion is said to be the king of beasts." is already in the passive voice.

Active voice:
People say that the lion is the king of beasts.

Explanation:
In the active voice, the doer of the action (in this case, "people") is made explicit.

The phrase "is said to be" is a passive construction that becomes "people say that..." in the active voice

The sentence "The book contains useful information." is in the active voice.

Passive voice:
Useful information is contained in the book.

Explanation:
The object "useful information" becomes the subject in the passive voice.

The verb "contains" (present simple) changes to "is contained" in passive form.

The sentence "Please keep off the green." is in the active voice and imperative form.

Passive voice:
You are requested to keep off the green.

Explanation:
Imperative sentences in passive voice are often changed using structures like "You are requested to...", "You are advised to...", or "Let..." depending on the tone.

"Keep off the green" means "do not step on the grass," and in passive, we use "You are requested to..." to keep the politeness and intent.

The sentence "One should take care of one's health." is in the active voice.

Passive voice:
One's health should be taken care of.

Explanation:
The object "one's health" becomes the subject in the passive voice.

The modal verb "should" is followed by "be + past participle" (i.e., "be taken care of").

Let us finish the game

Change the voice. (Passive) = Let the voice be changed.

Scarcely had I reached the station when he left.

I shall go to the cinema after I complete my work.