It was not until she could read and write when she was allowed to use smartphone19/50Mark 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. It was not until she could read and write when she was allowed to use smartphone.not untilwhenalloweduseGiải thíchĐáp án B. Đổi when thành that Cấu trúc: It was not until … that + S-V.