9. Find the product: (x + y + z) (x + y + z)
A. x2 + y2 + z2 + 2xy + 2x2 + 2yz
B. x + y + 2 + xy + yz + XZ
C. x2 + y2 + z2 + 2x2 + 2yz + 2xy
D. none of the above​