Students should never___________to violence to solve any problems.

Đáp án C.
Tạm dịch: Học sinh tuyệt đối không nên dùng bạo lực để giải quyết bất cứ vấn đề gì.
C. resort to sth: phải động đến ai, viện đến, nhờ tới ai/cái gì.
Các lựa chọn còn lại không phù hợp:
A. exert sth: dùng, sử dụng (sức mạnh, ảnh hướng)
Ex: - The moon exerts a force on the earth that causes the tides.
- He exerted all his authority to make them accept the plan.
exert oneself: cố gắng, ráng sức
Ex: In order to be successful he would have to exert himself.
B. resolve on sth/doing sth/ to do sth/ (that): kiên quyết
Ex: - We had resolved on making an early start.
- He resolved not to tell her the truth.
- She resolved (that) she would never see him again.
D. have recourse to sb/sth: nhờ cậy ai, cái gì.
Ex: - The government, when necessary, has recourse to the armed forces.
- She made a complete recovery without recourse to surgery.