英文tense的問題

過去進行式 Past continuous tense 是由 (was, were + 現在分詞) 而組成
表示動作作"過去"某一個動作發生時, 它正在正進行.
e.g. She was playing the piano when I called on her.
當我拜訪她的時候, 她正在彈鋼琴
(註) 彈鋼動作在拜訪時正在行.

過去完成 Past perferct tense 是由(had + 過去分詞) 組成, 它的用法比現在完成式簡明, 所以較易學會。
凡是兩個"過去"動作, 如果發生有先后時, 發生在先者用"過去完成式, 發生后者用"過去式。
e.g. When he teleponed, I had finished dinner
他打電話時, 我已吃完晚餐了
(註) 晚餐已於打電話之前已完成

past continous tense:when

Past perfect tense:since ,for, berfore

we use when to talk about what we were doing at this time something happened
eg1:when Alan was having breakfast,he smelled snoke(過去正在做)


eg2:i have collected old toys for about 20 years.(過去和現在都有做)

Past perfect tense
by the time, before, when~
eg.i had finished when the manager arrived.
you had returned before the show began.
we had not left by the time it stopped raining.

Past continuous tense had passing
Past perfect tense had done

Past tense present participle
1.answers answering
2.asked asking

Past continuous tense : had passing
Past perfect tense : had done