Final answer:
In indirect speech, the sentence 'The boy said, 'I had to go.'' becomes 'The boy said he had to go.', making option C correct.
Step-by-step explanation:
The sentence 'The boy said, 'I had to go.' when changed into indirect speech should be: The boy said he had to go. So, the correct option is C. The other options change the tense inappropriately for standard indirect speech conversions. When changing sentences from direct to indirect speech, it's important to consider the tense, pronoun, and wording changes needed to maintain the original sentence's meaning without direct quotation.