Which is true about the degree of the sum and difference of the polynomials
3x^5y - 2x^3y^4 - 7xy^3 and -8x^5y + 2x^3y^4 + xy^3 ?

Answers:
Both the sum and difference have a degree of 6
Both the sum and difference have a degree of 7
The sum has a degree of 6, but the difference has a degree of 7
The sum has a degree of 7, but the difference has a degree of 6