Simplify: (3x^2 - 4xy + 7y^2) - (7x^2 - 6xy - 3y^2)
A-4x^2 - 10xy - 10y^2
B-4x^2 - 2xy + 10y^2
C-4x^2 - 10xy + 10y^2
D-4x^2 + 2xy + 10y^2
A-4x^2 - 10xy - 10y^2
B-4x^2 - 2xy + 10y^2
C-4x^2 - 10xy + 10y^2
D-4x^2 + 2xy + 10y^2