The at the military academy is so rigid that students can hardly bear it.A. conventionB.

问题补充：

The at the military academy is so rigid that students can hardly bear it.

A. convention

B. confinement

C. principle

D. discipline

答案：

A. convention

B. confinement

C. principle

(答案→)D. discipline

解析：句意：军事院校的纪律如此的严格以至于学生们几乎不能忍受。convention常规；confinement限制；principle原则；discipline纪律。故选 D。