过去进行时 — 英语选择题
题目
At 7:20 yesterday morning, the school bus arrived. Mia started to pack her bag at 7:10 and finished at 7:30. Which sentence describes what Mia was doing when the bus arrived? A. Mia packed her bag. B. Mia was packing her bag. C. Mia is packing her bag. D. Mia packs her bag.