Why Would It Be Reasonable to Treat Strep Throat but Not

Why would it be reasonable to treat strep throat but not diphtheria with antibacterial antibiotics?

A) The signs and symptoms of diphtheria are mostly caused by the exotoxin produced by the causative agent. An antibiotic won't affect the exotoxin.
B) The signs and symptoms of strep throat are mostly from the exotoxin produced by the causative agent. An antibiotic effectively eliminates these exotoxins.
C) The causative agent of diphtheria is a virus, not a bacterium. The drug would have no effect against this infectious agent.
D) There are no antibiotics that have proven effective against the bacterium that causes diphtheria.
E) The causative agent of diphtheria is pleomorphic and does not have a cell wall. There are thus no antibiotics that would be effective against this organism.