The Best Way to Ensure That Your Son Will Continue

The best way to ensure that your son will continue to clean his room once he has started doing it is to

A) reward him some, but not all, of the times he cleans his room.
B) reward him every time he cleans his room.
C) reward him with money or new video games.
D) punish him every time he fails to clean his room.
E) never reward him other than to expect him to gain his own personal benefits from cleaning his room.