Which of the following is the correct expansion of $$(x + y + z)^{2}$$

A

$$ xy^{2} + yz^{2} + zx^{2} + 2 xy + 2 yz + 2 zx$$

B

$$xyz^{2} + x^{2} + y^{2} + x^{2} + 2 xy + 2 yz + 2 zx$$

C

$$x^{2} + y^{2} + z^{2} + 2 xy + 2 yz + 2 zx$$

D

None of these