If You Examine a Natural Population of Bacteria,it Is Common

Multiple Choice

If you examine a natural population of bacteria,it is common to find some antibiotic-sensitive and some antibiotic-resistant strains,even if the population has never been exposed to any antibiotic.Which explanation could account for this situation?

A) The resistant strain developed as a mutation and had no negative effect on fitness.
B) Selection favored the resistant strain and maintained it in the population so that it would be prepared for future antibiotic exposure.
C) The resistant strain had greater fitness compared to sensitive strains when the antibiotic was absent.
D) none of these
E) all of these