Step 1: Understanding passive sentence.
Passive: "Chicken is to be eaten by Suchi."
Here, subject = Chicken (receiver of action), agent = Suchi (doer).
Step 2: Converting to active voice.
Active form: "Suchi is to eat chicken."
Subject (Suchi) performs the action (eat) on object (chicken).
Step 3: Checking options.
(A) Wrong — "must" changes meaning.
(B) Wrong — incorrect word order.
(C) Correct — "Suchi is to eat chicken."
(D) Wrong — incomplete and ungrammatical.
Step 4: Conclusion.
Correct answer is (C) Suchi is to eat chicken.