Lets check all the choices:
A. subtraction:
(3x+2)-(4y-11)=3x+2-4y+11=3x-4y+13
similarly, (4y-11)-(3x+2)=-3x+4y-13
both are polynomials (of 2 variables)
B. (3x+2)(4y-11)=12xy-33x+8y-22, which is a polynomial
C. (3x+2)+(4y-11)=3x+2+4y-11=3x+4y-9, which is a polynomial
D.
both

and

are rational expressions in 2 variables, not polynomials
Answer: D