Final answer:
The completely simplified sum of the polynomials 3x²y² - 2xy⁵ and 43x²y² + 3xʸ is a trinomial with a degree of 6.
Step-by-step explanation:
The completely simplified sum of the polynomials 3x²y² - 2xy⁵ and 43x²y² + 3xʸ is:
(3x²y² - 2xy⁵) + (43x²y² + 3xʸ) = 3x²y² - 2xy⁵ + 43x²y² + 3xʸ
Combining like terms, we have: 46x²y² + 3xʸ - 2xy⁵
Therefore, the completely simplified sum of the polynomials is a trinomial with a degree of 6, so the correct answer is B. The sum is a trinomial with a degree of 6.