Question Set #3 (6 questions)

Please help I just need answers. Please save each of your answers along the way. (Question 12-16 are the pictures and are in order; question set one (1-6) is: and question set two (7-11, 17) is:

18) Which statement justifies that 3x² − 2x − 4 multiplied by 2x² + x − 3 obeys the closure property of multiplication?
A) The result 6x⁴ − 2x² + 12 has a degree of 4.
B) The result 6x⁴ − 2x² + 12 is a trinomial.
C) The result 6x⁴ − x³ − 19x² + 2x + 12 is a polynomial.
D) The result 6x⁴ − x³ − 19x² + 2x + 12 has a degree of 4.