🔹 S + had + V3 (past participle)→ She had left before I arrived.
🔹 S + had not (hadn’t) + V3→ He hadn’t eaten anything when I met him.
🔹 Had + S + V3?→ Had you studied English before 2010?
before, after
by the time, when, already, just, never, once
Ví dụ: → By the time I got there, they had gone. → She had already finished the test.
Chỉ dùng quá khứ hoàn thành khi có 2 hành động trong quá khứ, để phân biệt thứ tự.
Nếu không có hành động nào xảy ra sau, không cần thì quá khứ hoàn thành.
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