Solution:(c) The teacher said to me, "Why did you reach the examination hall so late?" (Correct)(a) The teacher said to me, "Why are you reaching the examination hall so late?" (Incorrect Tense)
(b) The teacher said to me, "Why had I reached the examination hall so late?" (Incorrect Pronoun)
(d) The teacher said to me, "Why you reached the examination hall so late?(Incorrect sentence structure)