Which polynomial correctly combines the like terms and expresses the given polynomial in standard form?9xy3 – 4y4 – 10x2y2 + x3y + 3x4 + 2x2y2 – 9y4

Combine the like terms: −10x²y² + 2x²y² = −8x²y², and −4y⁴ − 9y⁴ = −13y⁴. In standard form, arrange the degree-4 terms from highest power of x to lowest: 3x⁴ + x³y − 8x²y² + 9xy³ − 13y⁴. This matches choice D; choice C has the same terms but does not arrange them in standard form.

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