Leonard Is Addicted to Heroin,but Is Very Careful About Overdosing

Multiple Choice

Leonard is addicted to heroin,but is very careful about overdosing.He always uses a specific amount and takes it only in his apartment.This Friday,he got desperate for the drug while visiting a friend.This was the first time he used heroin outside his own apartment.He injected his normal "safe" dose of heroin but almost died of an overdose.According to the principles of classical conditioning what led to Leonard's condition?

A) Leonard's friend switched his drugs in order to teach him not to use drugs by switching his US with his CS.
B) The effect of the heroin was increased because Leonard injected it in a strange environment and his body could not use the stimuli in his basement to prepare for it.
C) Leonard's drug tolerance had reached its limits and his US was confounded with his CS and UR.
D) Leonard took his dose too soon and his body already had too much.