Answer:
Extinction of behavior maintained by positive reinforcement
Step-by-step explanation:
Every time Timmy´s mom complies with the screaming and delivers him the drink she is rewarding and reinforcing his negative behavior.
To reverse the situation, Timmy´s mom should use the extinction of behavior by positive reinforcement, which is to consistently ignore the negative behavior over time
until the child realizes that those same actions won´t produce the same results anymore.