There Is Often Cross-Sensitivity and Cross-Resistance Between Penicillins and Cephalosporins

There is often cross-sensitivity and cross-resistance between penicillins and cephalosporins because:

A) Renal excretion is similar in both classes of drugs.
B) When these drug classes are metabolized in the liver they both produce resistant enzymes.
C) Both drug classes contain a beta-lactam ring that is vulnerable to beta-lactamase-producing organisms.
D) There is not an issue with cross-resistance between the penicillins and cephalosporins.