1. When was Mike reading the document? ( at 6 o'clock là thời gian nên dùng when )
2. Where was Sarah waiting for him? ( the park để chỉ 1 địa điểm , dùng where )
3. What were the students talking about?
4. Who was writing the letter?( secretary là người , dùng who )
5. What was Lisa looking for?
Good luck!!