每个公民都有责任保卫自己的国家免受入侵。

Every citizen has a duty to ___defend their country from invasion.

她参加了自卫课程，学习如何在必要时保护自己。

She took a self-defence class to learn how to ___defend herself if necessary.

我们的免疫系统致力于保护身体免受病毒和细菌的侵害。

Our immune system works to ___defend the body against viruses and bacteria.