staple

面包是我们家早餐的主食。

Bread is a ___staple in our family's breakfast.

我需要订书钉把这些纸钉在一起。

I need a ___staple to fasten these papers together.

茶叶一直是这个山区的主要经济作物。

Tea has been the main economic ___staple in this mountainous area.