The train to Ho chi Minh city left at precisely 7 o’clock as usually, but the train

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.

The train to Ho chi Minh city left at precisely 7 o’clock as usually, but the train to Ha Noi capital left at half past six o’clock, which was exactly 20 minutes late.