Determine Whether or Not the Function Is Linear $C ( x ) = 485 + 68 x$

Determine whether or not the function is linear. If it is, determine the slope and interpret it.
-The cost of tuition at a community college is given $C ( x ) = 485 + 68 x$ x, where x is the number of credit hours. Find and interpret the C-intercept of the graph of this function.

A) 485; There is a tuition fee of $485 in addition to the charge per credit hour.
B) 68; There is a tuition fee of $68 in addition to the charge per credit hour.
C) 485; The tuition increases by $485 for each additional credit hour.
D) 68; The tuition increases by $68 for each additional credit hour.