Final answer:
Competitive inhibition occurs when an inhibitor competes with the substrate for binding to the active site of an enzyme, keeping the Vmax the same but increasing the Km. It is distinct from noncompetitive and other types of inhibition. Option A is correct.
Step-by-step explanation:
When competitive inhibition occurs, Vmax stays the same, but Km must increase. Competitive inhibitors bind reversibly at the active site of an enzyme, competing with the substrate for binding. However, this inhibition can be overcome by increasing the substrate concentration, which allows enzyme activity to reach the normal maximum rate.
Noncompetitive inhibitors, on the other hand, reduce the maximum rate of enzyme activity because they bind to an allosteric site, which changes the shape of the enzyme and its active site. As a consequence, no matter how much substrate is added, Vmax cannot be reached as it is with a competitive inhibitor.
This differentiates competitive inhibition from other types such as noncompetitive, uncompetitive, or mixed inhibition.