在马拉松的最后几英里，他的速度慢了下来，因为他开始感到疲劳了。

During the final miles of the marathon, his pace slowed as he began to ___tire.

这个要求苛刻的项目让我筋疲力尽。

This demanding project has completely ___tired me ___out.

老师变换了上课方式，以免让学生们感到疲倦。

The teacher varied her lessons so as not to ___tire her students.