Which polynomial is in standard form?
A)2xy^3+3x^3y^4-4x^4y^5+9x^5y^6
B)8x^5-5y^4-2xy^5+x^2y
C)x^3y^2-3x^2y-9x^4y^3+11x
D)5x^7y^2+7x^6y^5-14x^3y^7+51x^2y^9