What is the value of $$x^2 + 4y^2 + z^2 - 4xy + 4yz - 2xz$$?

A

$$(x + 2y - z)^2$$

B

$$(x - 2y + z)^2$$

C

$$(2y - x + z)^2$$

D

$$(2x - y + z)^2$$