Kara was out jogging and, despite being tired, decided to run one more mile. Based on her actions, economists would conclude that Kara:

A.must be an avid runner

B.decided that the marginal benefit of running one more mile would outweigh the cost of the additional mile

C.was not very tired, so the marginal cost of the extra mile was very low

D.decided that the marginal cost of running one more mile would outweigh the benefit of the additional mile