Any arithmetic operation on polynomials except division* will result in a polynomial. Appropriate choices are ...
A. (x^2+2) (x-1)
C. (x+1) plus (X^2-3X -2)
D. (X +5)-(3X +6)
E. (4/8)x . . . . . but not if you mean 4/(8x)
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* For division, the result may be a polynomial. In the specific example given here for B, it is not.