Ali decides to attend the one hour review session for microeconomics instead of working at his job. His job pays him $10 per hour. Aliʹs opportunity cost of attending the review session is
A.
the $10 he could have earned at his job.
B.
the value of the session minus the $10 he could have earned at his job.
C.
nothing, because the review session does not cost anything.
D.
equal to the benefit he gets from the review session.
E.
the one-hour review session.