Which of the following shows that polynomials are closed under subtraction when polynomial 5x − 6 is subtracted from 3x2 − 6x 2? 3x2 − 11x 8; may or may not be a polynomial 3x2 − 11x 8; will be a polynomial 3x2 − x 4; may or may not be a polynomial 3x2 − x 4; will be a polynomial.