Does anyone know the answer to this? i’m really struggling

D is the right answer

Multiply like you would multiply numbers.
First, use the 4 of the second line and multiply by each term of the first polynomial.
Then take the -2x term of the second polynomial and multiply by each term of the first polynomial. Write each term lined up under a term of the same degree.
Then multiply 3x^2 by each term of the first polynomial and agian, line up the degrees.
Finally, add like terms.

                                      x^2 + 5x + 1
                                    3x^2  - 2x + 4
*
                                   4x^2 + 20x + 4
                      -2x^3 - 10x^2 -   2x
          3x^4 + 15x^3 + 3x^2
+
          3x^4 + 13x^3 - 3x^2 + 18x + 4