This question assesses your knowledge of converting direct interrogative sentences into indirect speech. When transforming "She said, 'Do you know the answer?'" into indirect speech, specific rules for questions must be followed.
Firstly, the reporting verb "said" changes to "asked" because it's a question. Secondly, for yes/no questions (questions that can be answered with a simple 'yes' or 'no'), we introduce the reported clause with "if" or "whether." This acts as a conjunction, replacing the inverted subject-verb structure of the direct question.
Thirdly, the tense of the verb in the reported clause must be backshifted. The present simple "do you know" becomes the past simple "I knew." The auxiliary verb "do" is dropped, and the main verb "know" changes to its past tense form "knew."
Finally, the pronoun "you" changes to "I" to reflect the perspective of the person being reported to. The word order also changes from interrogative to assertive. Thus, "She asked if I knew the answer" correctly applies all these transformations. Options B, C, and D contain errors in tense, reporting verb, or conjunction usage.