1.Cấu trúc thì Quá khứ hoàn thành
Khẳng định:Chủ ngữ + had + past participle
----:I, You, He, She, We, They had finished before I arrived----
Phủ định:Chủ ngữ + had + not (hadn’t) + past participle
----:I, You, He, She, We, They hadn’t eaten before he finished the job:----
Nghi Vấn:Từ để hỏi + had + Chủ ngữ + past participle
----:What -> had he, she, you, we, they thought before I asked the question?:----
2.dấu hiệu nhận biết
Từ nhận biết: until then, by the time, prior to that time, before, after, for, as soon as, by, ...
Trong câu thường có các từ: before, after, when by, by the time, by the end of + time in the past …