Question 34:  It’s obligatory for teachers to change their teaching methods.

A. Teachers should change their teaching methods.

B. Teachers must change their teaching methods.

C. Teachers may change their teaching methods.

D. Teachers need to change their teaching methods.

Chọn đáp án B – Kiến thức: Modal verb

Giải thích: “It’s obligator”: đó là bắt buộc => must

Dịch: Các thầy cô phải thay đổi phương pháp giảng day của mình.