Step 1: Recognize tense.
"Helped" is past simple active.
Step 2: Convert to passive.
Object "Ranju" becomes subject: Ranju was helped by Ramesh.
Step 3: Evaluate.
(A) Wrong tense and grammar.
(B) Wrong form — "had to be helped" changes meaning.
(C) Wrong tense — present continuous.
(D) Correct — simple past passive.
Step 4: Conclusion.
Correct answer is (D).