三、重点语法。
过去进行时
1. 过去进行时的构成和基本用法
过去进行时由“was/were+动词-ing”构成，表示在过去某一时刻或某一段时间正在进行的动作，也可用来为一个或一系列动作的发生提供背景。过去进行时既可用在主句中，也可用在从句中，还可以同时用在主句和从句中。
2. 一般过去时与过去进行时用法的比较
一般过去时表示在过去某个时间发生过的动作或存在的状态，而过去进行时则表示在过去某一时刻或某一段时间正在进行的动作。
语法附加小练习。
1. 用所给词的适当形式填空。
(1)Sally took a photo of her classmates while they (play)games.
(2)I was doing my homework when you (call)me last night.
(3)My mother (cook)while I (do)chores at that time yesterday.
2. 翻译句子。
(1)大卫昨晚给他的朋友写了封信。

(2)大卫昨晚一直在给他的朋友写信。

三、重点语法。
1. (1) were playing (2) called
(3) was cooking, was doing
2. (1) David wrote a letter to his friend last night.
(2) David was writing a letter to his friend last night.

【解析】
1. 用所给词的适当形式填空：
(1) while引导时间状语从句，强调主从句动作同时发生，主句为一般过去时，从句要用过去进行时，主语they是复数，故填were playing。
(2) when引导时间状语从句，call是短暂性动作，此处表示过去某个时间点发生的动作，用一般过去时，故填called。
(3) while连接两个过去同时进行的动作，都要用过去进行时，主语My mother是第三人称单数，第一空填was cooking；主语是I，第二空填was doing。
2. 翻译句子：
(1) 该句表示过去发生的一次性动作，用一般过去时，故翻译为David wrote a letter to his friend last night.
(2) 该句强调过去某段时间一直在进行的动作，用过去进行时，故翻译为David was writing a letter to his friend last night.
【答案】
1. (1) were playing (2) called
(3) was cooking, was doing
2. (1) David wrote a letter to his friend last night.
(2) David was writing a letter to his friend last night.
【知识点】
过去进行时用法、一般过去时与过去进行时辨析
【点评】
本练习围绕过去进行时展开，考查了过去进行时的构成、基本用法以及与一般过去时的区分，帮助学习者巩固对这两种过去时态的理解与运用，提升时态辨析和实际运用能力。
【难度系数】
0.7