音乐课上，老师教我们如何用手指拨动竖琴的琴弦。

In music class, the teacher showed us how to pluck the strings of the ___harps with our fingers.

她总是没完没了地唠叨孩子的成绩问题，却不给出任何建设性建议。

She constantly ___harps on her child's grades without giving any constructive advice.