在制作电路板之前，我们需要选择合适的基材。

Before making the circuit board, we need to choose the right ___substrate.

这种酶需要特定的底物才能发挥作用。

This enzyme requires a specific ___substrate to function properly.

这种新型材料被用作电子元件的基底。

This new material is used as the ___substrate for electronic components.

这些苔藓生长在岩石表面，岩石为它们提供了必要的生长基质。

These mosses grow on the rock surface, which serves as their essential ___substrate.