Which experimental result would best demonstrate that trimethoprim is a competitive inhibitor of dihydrofolate reductase (enzyme B)?

Increasing dihydrofolic acid concentration in enzyme kinetics assays reduces the degree of inhibition by trimethoprim and increases apparent Km without changing Vmax.

Trimethoprim increases the transcription of dihydrofolate reductase, and simultaneous addition of large substrate amounts enhances inhibition, demonstrating competitive binding.

Trimethoprim permanently denatures dihydrofolate reductase, which can be reversed by dialysis, proving competitive reversible binding.

Trimethoprim reduces Vmax but does not change Km in enzyme assays, which is the hallmark of competitive inhibition.