Which polynomial represents the sum below?

(-x4 + 4x3 + 1) + (4x3 + x + 2)

A. -x4 + 4x6 + x + 3
B. x8 + 8x7 + x + 3
C. -x7 + 8x6 + x + 7
D. -x4 + 8x3 + x + 3