Simplify.
(x^2 + 5^x + 8)(x^2 + 2^x + 6)

A. x4 + 10x2 + 48
B. x4 + 2x3 + 6x2 + 7x + 14
C. 2x2 + 7x + 14
D. x4 + 7x3 + 24x2 + 46x + 48
Can you also explain?