One Reason That Aversive Conditioning May Only Be Temporarily Effective

One reason that aversive conditioning may only be temporarily effective is that

A) for ethical reasons, therapists cannot use sufficiently intense unconditioned stimuli to sustain classical conditioning.
B) patients are often unable to become sufficiently relaxed for conditioning to take place.
C) patients know that outside the therapist's office they can engage in the undesirable behavior without fear of aversive consequences.
D) most conditioned responses are elicited by many nonspecific stimuli and it is impossible to countercondition them all.