She said that she________all day last Saturday.A.worked B.would work C.was working D.had workedShe said that she________all day last Saturday.A.worked B.would work C.was working D.had worked那A为什么不对呢?也有这种说法：It rained all day last Saturday.Mary stayed at home all day last Saturday.这道题为什么不选A呢?

表示过去某段时间正在进行的动作.
Shirley was writing a book about China last year but I don't know whether she has finished it.舍利去年在写一本有关中国的书,但我不知道他是否完成.
They were building a dam last winter.去年冬天他们在建大坝.
一般过去时与过去进行时用法比较
一般过去时表示在过去某个时间发生的动作或存在的状态（强调一次性动作）；而过去进行时则表示在过去某一时刻或某段时间正在进行的动作（强调反复的动作）.
Mary wrote a letter to her friend last night.玛丽昨晚给她的朋友写了封信.（写完了）
Mary was writing a letter to her friend last night.玛丽昨晚一直在给她的朋友写信.（不一定写完）
We built a bridge last winter.去年冬天我们修了一座桥.（建成了）
We were building a bridge last winter.去年冬于我们在修一座桥.（一直在修,不涉及结果）