我们进行随机检查以让每个人保持警惕。

We have random inspections to ___keep everyone ___on ___their ___toes.

项目的不断变化让团队保持警惕。

The constant changes in the project ___keep the team ___on ___their ___toes.

为了让学生们保持警惕，老师进行突击测验。

To ___keep the students ___on ___their ___toes, the teacher gives pop quizzes.