Unit 3 what were you doing when the ufo arrived? 【重难点分析】一. 过去进行时过去进行时表示过去某一时刻或者某段时间正在进行或发生的动作，常和表过去的时间状语连用。 过去进行时的构成：肯定形式：主语+was/were+V-ing否定形式：主语+was not (wasnt)/were not (werent)+V-ing疑问形式：Was/Were+主语+V-ing。基本用法：1. 过去进行时表示过去某一段时间或某一时刻正在进行的动作。常与之连用的时间状语有：at that time/moment, (at) this time yesterday (last night/Sunday/week), at+点钟+yesterday (last night / Sunday)，when sb. did sth等时间状语从句。如： What were you doing at 7p.m. yesterday? 昨天晚上七点你在干什么？
