Efficiency occurs only at that output where: A. marginal benefit exceeds marginal cost by the greatest amount.
B. the areas of consumer and producer surplus are equal.
C. consumer surplus exceeds producer surplus by the greatest amount.
D. the combined amounts of consumer surplus and producer surplus are maximized.

Penny poodle wanted to know which dog obedience training program was more effective: puppy pride, the approach she has been using for any years, or doggie do-right, a new approach. penny convinced 50 human companions of untrained dogs to participate in her study. the dogs and their humans were randomly assigned to complete the puppy pride or doggie do-right course. at the end of the training programs, all of the dogs were scored on their level of obedience on a standardized dog obedience checklist (scores could range from 10 to 100). the design of this study is: