Answer:
5 is a constant. (it has no variables)
x + 2 is not a constant. It does, however, have two terms, x and 2.
(terms are seperated by addition/subtraction)
This rules out a and b.
As for c... 5(x+2) implies multiplication, which would be a product, not a sum.
The product of a constant factor 5 and a 2-term factor x+2
Explanation: