【单选题】— Has Sam finished his homework today? — I have no idea. He ________ it this morning.
【单选题】—Has Sam finished his report? —I have no idea. He _______ it in his office the whole morning.
【简答题】— Has Sam finished his homework today, Anne? — I have no idea. But he ________ it this morning. [ ] A .did B. had done C. was doing D. had done