Chọn câu đúng

A. ${\left(x-y-z\right)}^2=x^2+y^2+z^2+2xy+2yz-2zx$

B. ${\left(x-y-z\right)}^2=x^2+y^2+z^2$

C. ${\left(x-y-z\right)}^2=x^2+y^2+z^2-2xy-2yz-2zx$

D. ${\left(x-y-z\right)}^2=x^2+y^2+z^2-2xy+2yz-2zx$