由于多项式A=x 2+2y 2-z 2,B=-4x 2+3y 2+2z 2且A+B+C=0,
则C=-A-B=-(x 2+2y 2-z 2)-(-4x 2+3y 2+2z 2)=-x 2-2y 2+z 2+4x 2-3y 2-2z 2=3x 2-5y 2-z 2.
故选B.
由于多项式A=x 2+2y 2-z 2,B=-4x 2+3y 2+2z 2且A+B+C=0,
则C=-A-B=-(x 2+2y 2-z 2)-(-4x 2+3y 2+2z 2)=-x 2-2y 2+z 2+4x 2-3y 2-2z 2=3x 2-5y 2-z 2.
故选B.