66. I am allowed to visit my classmates at the weekend.

->   be allowed to do sth

67. They have learned/have been learning English for ten years.

-> S+started..... khoảng thời gian +ago  (thì quá khứ) -> S+ have/has+V3/-ed.... for + khoảng thời gian (hiện tại hoàn thành)

68. I think that I should do voluntary work.

-> it's a good idea for me to do .... ->  I should do....

69.It was Anna's boyfriend's sense of humour that she couldn't understand.

->câu chẻ/nhấn mạnh (cleft /emphasis sentence)

-> It is/was .......  that/who ..........

70.  Had he studied hard, he wouldn't have failed the exam

->câu điều kiện loại 3 rút gọn

If he had studied hard, he wouldn't have failed the exam

->Had he studied hard, he wouldn't have failed the exam

->ta bỏ "if", đem "had" lên trước chủ từ "he"

-> Had +S +V3/-ed......,  S'+would(not)/could(not)+have +V3-ed.......