Question

each enzyme only has 1 substrate that will fit its active site. what is this called? catalyst fragile specific reusable

Explanation:

The question is about enzyme properties. Enzyme specificity means each enzyme's active site is specific to one substrate (or a few similar ones) that fits it, matching the description "each enzyme only has 1 substrate that will fit its active site". "Catalyst" refers to enzyme's role in speeding up reactions, "fragile" relates to sensitivity to conditions, and "reusable" means enzymes aren't used up, none matching the specificity concept here.

Answer:

specific