Answer:
D. the marginal cost of the last barrel is just equal to the price buyers are willing to pay for that last barrel.
Step-by-step explanation:
In the case of the oil market that oil is to be supplied to the point where the marginal cost of the previous barrel should be equivalent to the price where the pruchaser want to pay for that previous barrel
So as per the given situation, the option d is correct
ANd, the rest of the options seems incorrect