I need HELP Quick!!!

If f(x) = x + 5, what does f(8) represent? (1 point)

A:The value of x when (x + 5) = 8

B:The value of 8f(x) when x = 8

C: The value of f(x) when (x + 5) = 8

D:The value of (x + 5) when x = 8