Her credits need to be AT LEAST EQUAL TO OR GREATER THAN 144 (credit hours) so we can eliminate choices B and D.
She already completed 4 semesters in which she receives 15 credit per semester.
This expression can be written as 4(15).
She needs to do a certain remaining hours of credit which can be represented by c and only c without any other coefficient.
So, the most reasonable choice here is A.