他不停地用指关节揉着发疼的太阳穴。

He kept ___knuckling his aching temples.

在父母的坚持下，他最终屈服并同意去上大学。

Under his parents' insistence, he finally ___knuckled down and agreed to go to college.

考试临近，她终于开始认真复习了。

With exams approaching, she finally started ___knuckling down to study.