Sam offered a treat to her son so he would behave while considered by psychologists. This is an example of:

The correct answer is D. incentive.

An incentive is something that motivates or encourages someone to do something. In this case, Sam is using a treat as an incentive to encourage her son to behave. It’s a way to reinforce positive behavior through a reward. If you have more questions or want to dive deeper into this topic, feel free to ask!