Choose the sentence which is in the passive voice:

The correct answer is Option (4) → The accident victim was taken to the hospital by the police

Passive voice:

• Object becomes subject: in the passive voice the receiver of the action becomes the subject; here "The accident victim" received the action.
• Tense kept: the verb takes the form be + past participle: was taken = was + past participle.
• Agent (by ...): the doer may follow with by: by the police.
  Example: The letter was written by my sister.

Why the Other Options are Incorrect?

Option 1: All his friends praised him — Incorrect. The doer "All his friends" is the subject and "praised" is a simple past verb: active voice.

Option 2: Renu planted many flowers in her garden — Incorrect. Renu does the planting: active voice.

Option 3: Many students watched the football match — Incorrect. The doers, "Many students", are the subject: active voice.