Which Statement About High Cocaine Responding (HCR) and Low Cocaine

Which statement about high cocaine responding (HCR) and low cocaine responding (LCR) rats is true?

A) HCR and LCR rats differ in their responses to cocaine despite being genetically identical.
B) LCR rats express more dopamine transporters in the nucleus accumbens and dorsal striatum than HCR rats.
C) HCR rats show greater levels of extracellular dopamine than LCR rats, under drug-free conditions.
D) When the animals are given a moderate dose of cocaine, extracellular dopamine levels increase more in the LCR rats than in the HCR rats.