我们进行了一次有益的讨论，帮助澄清了我们的目标。

We had a ___profitable discussion that helped clarify our goals.

她通过志愿服务和学习新技能充分利用了暑假。

She made ___profitable use of her summer break by volunteering and learning new skills.

这种方法被证明对快速提高语言流利度非常有益。

This method proved to be ___profitable for improving language fluency quickly.