An antibiotic that binds periplasmic beta-lactamases to inhibit them (a beta-lactamase inhibitor) is given in combination with a beta-lactam that targets transpeptidases. Why does this combination broaden effective coverage against some Gram-negative bacteria?

Because the combination physically disrupts the outer membrane by synergistic detergent action, irrespective of enzymatic activity.

Because beta-lactamase inhibitors increase porin channel size so that beta-lactams can diffuse through the outer membrane more easily.

Because the inhibitor neutralizes periplasmic enzymes that would otherwise hydrolyze the beta-lactam in the Gram-negative periplasm, allowing the beta-lactam to reach and inhibit transpeptidases, thereby restoring activity against otherwise resistant Gram-negative strains.

Because beta-lactamase inhibitors convert Gram-negative bacteria into Gram-positive forms, making them inherently more susceptible to beta-lactams.