A 15-year-old female was said to have Koplik's spots after a doctor's examination. This suggests that

A) she has measles caused by the rubeola virus.
B) no antibiotic is useful because it's a mixed infection.
C) she has a toxin-encoding phage that also encodes antibiotic-degrading enzymes.
D) the causative agent is a MRSA.
E) rapid necrosis of infected tissue has limited access to the antibiotic.