Task: Mark the letter A, B, C or D on your answer sheet to indicate the underlined part that needs correction in each of the following questions.

(Chọn một trong bốn đáp án A, B, C, hoặc D có chứa lỗi sai ở mỗi câu sau).

1.  After Mrs. Trang had returned to her house from work, she was cooking dinner.

           A                            B        C                                               D