Determine if the following equation is an identity (x + y + x)^2 = x^2 + y^2 + z^2 + 2xy + 2yz + 2zx
A. This is not an identity because the equation is true
B. This is an identitv because the equation is not true.
C. This is not an identity because the equation is not true.
D. This is an identity because the equation is true.