How Can Non-Drug Related Behaviors Such as Gambling and Viewing

How can non-drug related behaviors such as gambling and viewing pornography be considered addictions if no chemicals enter the human body?

A) The surge of dopamine caused by participation in these behaviors can motivate people to chase the feelings of pleasure and reward.
B) Because sex is a primary motivated behavior, by definition it is addictive
C) These behaviors are examples of secondary motivated behaviors that people strive to fill the need for, and dopamine is the reward system.
D) No scientific evidence has proven that these behaviors are actually addictive or even connected to the mesolimbic system.