The complement, F', of F(x, y, z) = (xy + z') + (x'z + y) (not simplified) is:

a. z'(x + y) + y(x' + z)
b. (x'y' + z) + (x'z' + y)
c. ((x' + y')z)((x + z')y')
d. (x + y + z')(x'yz)