Most students attending college pay tuition and are unable to hold a full-time job. For these students, tuition is
选项：

A:part of the opportunity cost of going to college. So are their forgone earnings from not holding a full-time job.
B:part of the opportunity cost of going to college. Their forgone earnings from not holding a full-time job are not part of the opportunity cost of attending college.
C:not part of the opportunity cost of going to college, but their forgone earnings from not holding a full-time job are part of the opportunity cost of attending college.
D:not part of the opportunity cost of going to college. Neither are their forgone earnings from not holding a full-time job.