记叙文中的过去进行时 — 英语选择题
题目
阅读下面的句子，选出括号内动词的正确形式。
While the printer (print) his new story, Mark Twain noticed that two boys (play) by the river and never looked at the paper in their hands.
A. was printing; were playing B. printed; played C. was printing; played D. printed; were playing