她每周都会磨一次菜刀。

She ___sharpens her kitchen knife once a week.

每天练习钢琴可以提高你的演奏技巧。

Practicing piano daily ___sharpens your playing skills.

柠檬的酸味让我的饥饿感更加强烈了。

The sour taste of lemon ___sharpens my hunger.