A college student is introduced to methamphetamine, eventually needs more and more to feel good, ...

A college student is introduced to methamphetamine, eventually needs
  more and more to feel good, and soon starts stealing to support her
  habit. She is expelled from school for stealing from her roommate.
 
  Why might she have become addicted so quickly?
  A. Methamphetamine converts to morphine in the brain and binds
  to endorphin receptors that cannot regulate the release of
  dopamine in her limbic system.
  B. She probably has a genetic defect that increases levels of
  naturally produced dopamine, and the drug decreases
  stimulation of her dopamine receptors.
  C. She probably has an abnormally low amount of naturally
  produced dopamine in her limbic system due to an addictionrelated genetic problem.
  D. Increased baseline levels of dopamine in the synapse between
  her VTA and ACC decreased stimulation of her dopamine
  receptors upon her first use.