在英语语法中，过去进行时是一种非常重要的时态，用于描述在过去某个特定时间点正在进行的动作或活动。为了帮助大家更好地掌握这一时态，下面将通过一系列练习题来加深理解，并附上详细的答案解析。
一、单项选择题
1. Last night at this time, I _______ my homework.
A) was doing B) did C) have done D) am doing
解析：此句表示昨晚这个时候我正在做作业，因此正确答案是 A) was doing。
2. When the phone rang, they _______ dinner.
A) ate B) were eating C) had eaten D) eat
解析：当电话响起时，他们正在吃晚饭，所以应该使用过去进行时，答案为 B) were eating。
3. She _______ a book when her mother came in.
A) read B) reads C) was reading D) is reading
解析：当她妈妈进来的时候，她正在读一本书，故选 C) was reading。
4. They _______ football when it started to rain.
A) play B) played C) were playing D) have played
解析：开始下雨时，他们正在踢足球，答案为 C) were playing。
5. I _______ TV with my friends when the power went out.
A) watched B) was watching C) watch D) am watching
解析：停电的时候，我和朋友们正在看电视，答案为 B) was watching。
二、改错题
6. He was sleeping while he studying for his exam.
改正：He was sleeping while he was studying for his exam.
解析：原句中“studying”形式错误，应改为“was studying”，以保持句子的一致性。
7. She was walking on the street when suddenly she fall down.
改正：She was walking on the street when suddenly she fell down.
解析：“fall”应改为过去式“fell”，因为动作发生在过去。
三、填空题
8. John _______ (write) a letter when his friend arrived.
答案：was writing
解析：描述过去某一时刻正在进行的动作，需用过去进行时。
9. We _______ (watch) TV when the news came on.
答案：were watching
解析：同样表示过去某一时刻正在进行的动作。
以上就是关于过去进行时的一些基础练习和解析。希望大家通过这些题目能够更加熟练地运用这一时态。继续努力学习，相信你的英语水平会有很大的提升！
