Question

enzymes only catalyze one reaction - the active site fits with only one substrate.

Explanation:

The statement describes enzyme specificity, where an enzyme's active site is specific to one substrate, so the term "Specific" matches this concept (active site specificity for one substrate), while "Active Site" is the region, "Neutral" doesn't relate, and "Protein" is the enzyme's nature but not about the reaction - substrate fit specificity.

Answer:

Specific