The past perfect continuous tense

(-) I had not been finding my door keys until you told me.

(?) Had you been cooking for 30 minutes before you had a bath? Yes, I had./No, I hadn’t.

(?) What had you been doing before you met her?

(+) S + had + been + V-ing... (-) S + had not + been + V-ing. (?) Had + S + been + V-ing? * Wh- + had + S + been+ V-ing?

Thì quá khứ hoàn thành tiếp diễn diễn tả một hành động quá khứ đã xảy ra và kéo dài cho đến khi hành động quá khứ thứ 2 xảy ra(hành động thứ 2 dùng Past Simple) thường khoảng thời gian kéo dài được êu rõ trong câu.

Eg. The man had been playing cards for 3 hours before I came

They had been living in London for ten years when I met them