Answer: A failure to earn social reinforcement associated with an "A".
Explanation: According to reinforcement theory, which is an integral part of behavioral theory, it argues that social behaviors are conditioned by external events. Such external events are outside the human psyche, so they absolutely come as an external factor, and people repeat certain behavior if accompanied by some external reinforcement that is pleasant, in Leslie's case it is usually A in tests. Such external factors, events, imply the removal of something unpleasant, that is, aversive, but if this happens, then there is a decline in the acquisition of pleasant reinforcements, the consequence can be depression.