To solve this problem, we need to analyze each statement regarding competitive inhibition in enzyme kinetics:$•$Option 1: A competitive inhibitor reacts reversibly with the enzyme to form an enzyme-inhibitor complex.$\newline$ - This statement is correct. In competitive inhibition, the inhibitor binds reversibly to the active site of the enzyme, forming an enzyme-inhibitor complex.$•$Option 2: In competitive inhibition, the inhibitor molecule is not chemically changed by the enzyme.$\newline$ - This statement is correct. The inhibitor binds to the enzyme but is not transformed by it, as it competes with the substrate for the active site.$•$Option 3: The competitive inhibitor does not affect the rate of breakdown of the enzyme-substrate complex.$\newline$ - This statement is correct. Competitive inhibitors do not affect the breakdown of the enzyme-substrate complex; they only compete with the substrate for binding to the enzyme.$•$Option 4: The presence of the competitive inhibitor decreases the Km of the enzyme for the substrate.$\newline$ - This statement is incorrect. In competitive inhibition, the apparent Km increases because a higher substrate concentration is required to achieve the same reaction rate as without the inhibitor.Therefore, the incorrect statement is Option 4.