If xy + yz + zx = 0, then (1x2−yz+1y2−zx+1z2−xy)(1x2−yz+1y2−zx+1z2−xy) (x,y,z≠0)=?(x,y,z≠0)=?

• A. 3
• B. 1
• C. x + y + z
• D. 0