The ascending or descending order of a polynomial is determined by the increasing or decreasing power of variable “x” respectively.
The question is to find about the polynomial in descending order, so in this case, the 3rd option is correct, i.e. 4x^2 – 3x + 9 or 4x^2 – 3x^1 +9x^0. The power of “x” decreasing from 2 to 1 and then finally to 0.