Operant behavior can, in general, be lumped into three functional classes. They are: a. may remove, avoid, or terminate a stimuli that results in an increase in the strength b. may produce stimuli that result in an increase in the strength of the operant behavior c. may add stimulus that strengthens the probability a behavior will not occur d. may produce or remove still other stimuli that fail to strengthen the operant behavior e. may produce stimuli that increased the probability a behavior will not occur