Final answer:
Deciding which college to attend is the decision for which marginal analysis is least beneficial.
Step-by-step explanation:
Marginal analysis is least beneficial for deciding which college to attend. When deciding between different colleges, there are often significant differences in factors like location, programs offered, and reputation, which make it difficult to make decisions based solely on marginal gains or losses. Other decisions listed, such as taking a lunch break or doing more sit-ups at the gym, can be evaluated more easily using marginal analysis because the benefits and costs are more clearly defined and measurable.