What is efficiency wage theory? select the correct answer below: a. the theory that workers' productivity depends on their pay, and so employers will often find it worthwhile to pay their employees somewhat more than market conditions might dictate. b. the theory that if an employer reacts to poor business conditions by reducing wages for all workers, then the best workers, those with the best employment alternatives at other firms, are the most likely to leave. c. the theory that argues that those already working for firms are "insiders," while new employees, at least for a time, are "outsiders."d. the theory that points out that even if most workers were hypothetically willing to see a decline in their own wages in bad economic times as long as everyone else also experiences such a decline, there is no obvious way for a decentralized economy to implement such a plan.