B. Assertion and reason both are correct statements, but the reason is not the correct explanation for the assertion.

C. The assertion is a correct statement, but the reason is the wrong statement.

D. Assertion and reason both are incorrect statements.

E. The assertion is a wrong statement, but the reason is the correct statement.

• Enzymes do have active sites that hold substrate molecules for certain chemical reaction in a living organism.

• This active site of enzymes usually holds the substrate molecule at a suitable orientation so that the substrate can interact with the reagent molecules.

• Substrates bind to the active sites through ionic bond, H-bonding, van der Waals interaction or dipole-dipole interaction.

Whereas, drugs inhibit the activities of enzymes by blocking the active sites & prevent the binding of the substrate to the site and thus disrupts the catalytic activity of enzymes.

• Therefore, drug’s competition with the suitable natural substrates by attaching covalently to active site of enzyme cannot be the reason for the given assertion statement.