时间状语从句
状语：说明地点、时间、原因、目标、结果、条件、方向、程度、方式和伴随状态。引导词： when, while, as, after, before, as soon as, since, till/untill, by the time...
When I left, it began to rain. When I saw him, he was drinking some tea. 当我抵达伦敦时候，天黑了下了。昨天晚上十点我正在看电视.当Mary正在做早饭时候，我正在看报纸