Each of the following statements concerning the mechanisms of resistance to antimicrobial drugs is correct EXCEPT:

  •  Resistance to some drugs is due to a chromosomal mutation that alters the receptor for the drug.
  •  Resistance to some drugs is due to transposon genes that code for enzymes that inactivate the drugs.
  •   Resistance genes are rarely transferred by conjugation.
  •   R factors are plasmids that carry the genes for enzymes that modify one or more drugs.