Once an Avoidance Response Has Been Learned,it Usually

Once an avoidance response has been learned,it usually:

A) extinguishes very quickly if we quit reinforcing it.
B) extinguishes very quickly if we have used a variable reinforcement schedule to create it.
C) is often very difficult to extinguish,even when aversive consequences have been removed.
D) is often very difficult to extinguish if we used a continuous reinforcement schedule to create it.