Answer: Choice A) An economic theory that is shared by the discipline of Psychology
Through the research I've found so far, the articles mention that economic choices have a psychological link. This is because economics is basically the study of human psychology (more or less) in terms of how to allocate resources and how best to use them. The law of diminishing marginal utility is basically the idea where the concept "more is always better" is simply not true. An example would be that you are at a restaurant and there's an endless buffet. The food isn't infinite and neither is the capacity of your stomach. After a certain point, you'll find that eating another burger isn't as satisfying as eating the first few burgers. You can think of it as a graph where the curve may start with a sharp increase, but eventually it levels off.
Side note: The term "affective habituation" may be used in psychology textbooks as something very similar to the law of diminishing marginal utility.
