Question

the region of an enzyme where the substrate binds is called
the active site.
the binding pocket.
the reaction site.
the catalyst site.
an analog.

Explanation:

In enzyme biology, the region where the substrate binds to the enzyme is defined as the active site. The other options: "binding pocket" is not the standard term, "reaction site" is incorrect (the active site is where binding and catalysis occur), "catalyst site" is not the correct term, and "analog" refers to a molecule similar to a substrate, not a binding region.

Answer:

A. the active site.