Sulfanilamide is an antimicrobial drug that mimics the shape of an important substrate for a particular bacterial enzyme and can bind in its active site, thereby inhibiting the enzyme. This type of inhibition is known as

A. Allosteric inhibition:
Allosteric inhibition involves a molecule binding at a site other than the active site to change enzyme activity; the described action is binding at the active site, so this does not match.

B. Competitive inhibition:
A competitive inhibitor resembles the substrate and competes for binding at the enzyme’s active site; binding prevents the actual substrate from occupying the active site, which fits the description of sulfanilamide.

C. Excitatory allosteric control:
This term implies activation via an allosteric site rather than inhibition at the active site and does not describe substrate mimicry binding the active site.

D. Noncompetitive inhibition:
Noncompetitive inhibitors bind at a different site and reduce enzyme activity regardless of substrate concentration; they do not typically resemble the substrate or compete for the active site.

E. Feedback inhibition:
Feedback inhibition occurs when an end product of a metabolic pathway inhibits an enzyme earlier in that pathway, usually via allosteric binding; the scenario describes direct active-site competition rather than pathway end-product regulation.