Question

enzymes are not a reactant or a product - they are able to be used again. active site, activation energy, lactose, reusable

Explanation:

The statement is about enzymes being reusable (not consumed as reactants or products, so can be used again). Among the options, "Reusable" directly relates to this property. "Active Site" is the enzyme's binding region, "Activation Energy" is what enzymes lower, and "Lactose" is a substrate, not related to the enzyme's reusability.

Answer:

Reusable