Choose the correct active voice : He was congratulated by his teacher on his brilliant success in the recent examination :
His teacher congratulated him on his brilliant success in the recent examination
Turning a passive sentence into the active voice follows a fixed procedure. The agent that appears after “by” becomes the subject, the subject of the passive sentence becomes the object, and the verb is put into the corresponding active tense. Nothing else in the sentence may be altered.
Here the agent is his teacher, so the teacher becomes the subject. The passive subject is “he”, which becomes the object and therefore takes its object form. The verb was congratulated is simple past passive, so the active form is the simple past.
One choice reverses the roles and makes the student congratulate the teacher, which changes the meaning completely. Another swaps the preposition, and the verb in question is normally followed by “on” before the achievement, so that version does not reproduce the original wording. A third drops the whole prepositional phrase and loses the information about the achievement altogether.
His teacher congratulated him on his brilliant success in the recent examination option is correct.