Avoidance Learning Is Somewhat Puzzling Because

Avoidance learning is somewhat puzzling because

A) it is an unlearned response developed through evolution to prevent harm to the organism, and yet it is readily modified by instrumental conditioning procedures.
B) the instrumental avoidance response cannot occur until the organism has first learned a classically conditioned fear contingency.
C) it is difficult to explain what reinforces the instrumental response and why avoidance responses are so resistant to extinction when the aversive outcome is omitted.
D) sometimes the avoidance S^D facilitates learning the instrumental avoidance response and sometimes it interferes with learning the instrumental avoidance response.