What does evolution mean? A A rapid change in the environment that causes a reduced gene pool.
B Selectively acquiring useful genes.
C A gradual change in characteristics over time.
D Changing characteristics to suit the environment over a short period of time.

Explanation:

Evolution may be defined as any net directional change or any cumulative change in the characteristics of organisms or populations over many generations—in other words, descent with modification… It explicitly includes the origin as well as the spread of alleles, variants, trait values, or character states

hope this helps

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme