微积分是理解物体运动变化的关键数学工具。

___Calculus is the key mathematical tool for understanding how objects move and change.

工程师使用微积分来计算桥梁的承重能力。

Engineers use ___calculus to determine the load-bearing capacity of bridges.

患者因为肾结石疼痛难忍而住院。

The patient was hospitalized due to severe pain caused by a kidney ___calculus.