Answer: The false statement is letter b.) PABA serves as the competitive inhibitor in the action of sulfanilamides.
Explanation: Sulfanilamides, correspond to antimetabolites which are synthetic compunds that resemble metabolites. In this case sulfanilamide resembles the metabolite PABA in structure, which is the one responsible for metabolizing folic acid. In this case it is sulfanilamide that serves as a competitive inhibitor and not the way around. However it is not the PABA metabolite that is affected directed in the process, sulfanilamide serves as the inhibitor of the enzyme dihydropteroate synthetase which serves as catalyzer for PABA.