If (xy)ᵃ⁻¹=z, (yz)ᵇ⁻¹=x, (xz)ᶜ⁻¹=y, and xyz is not -1,0 or 1, then which of the following is equal to ab+bc+ca?
a. abc
b. abc÷2
c. 2abc
d. 3abc