如果我们没有军队，我们怎么能保卫我们的家园？

How can we ___defend our homeland if we don't have an army?

我去上空手道课学习如何保护自己。

I'm going to karate lessons to learn how to ___defend myself.

白细胞帮助身体防御感染。

White blood cells help ___defend the body against infection.