It was not until the students were seated ______ the proctor realized he

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Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions.

It was not until the students were seated ______ the proctor realized he had the wrong test booklets.

as soon as

that

and

when

Giải thích

Đáp án B

Cấu trúc: It….not until….that: Mãi cho đến khi

Tạm dịch: Mãi cho đến khi sinh viên được xếp chỗ xong thì giám thị mới nhận ra ông ấy có nhầm sách kiểm tra