当牛奶用完了，豆浆可以作为很好的替代品。

When milk runs out, soy milk can be a good ___substitute.

椰子油常被用作黄油的健康替代品。

Coconut oil is often used as a healthy ___substitute for butter.

老师生病时，学校安排了代课老师来顶替。

The school arranged a ___substitute teacher when the regular one was sick.