when did it start? 解释

when did it start? 解释 When did it start? It's raining .when did it start? -It's raining!When did it start? 是when did it started还是when did it start? 要解释说明.（32）--It's still raining!When did it start?---I don't When did it start?About ______ ago. When did it start?为什么did用过去式? When did it start?About ______ago.怎么填? when did you start doing it?请翻译 自学英语,When did it start raining.一个句子里的start doing是怎么回事? when did you start to______?