Enzyme-Substrate Shape Mismatch Steps:

• Sucrose fits sucrase's active site due to complementary 3D shape.
• Sucralose replaces three OH groups with Cl atoms, altering molecular geometry.
• Enzymes require precise shape match for binding (lock-and-key model).
• Shape change prevents sucralose from entering or binding to active site.

Why A is correct:

• Lock-and-key hypothesis states active site shape must complement substrate; Cl atoms distort sucralose, eliminating fit.

Why the others are wrong:

• B: Binding failure affects entire molecule, not just modified fructose part.
• C: Induced fit requires initial binding, which shape mismatch blocks first.
• D: Fewer H-bonds may contribute, but core issue is overall shape incompatibility.

Final answer: A