Question

John pays $35 to have quick oil and filter change his car's oil every few months. he could change his own oil, but the time that it requires would cost john far more than $35. this is an example of:

Answer 1

A: No. We don't know who has an absolute advantage at oil changing- the problem doesn't say.
B. Yes. John specializes in whatever he does, and the oil company specializes in changing oil, and both benefit.
C. No. There are no restrictions on trade in this case.
D. No. Opportunity cost is a factor in the problem, but it's increasing, not decreasing.

So B is your answer (Comparative Advantage)

Answer 2

Opportunity cost would be the answer.