The elements 'X', 'Y' and 'Z' form oxides which
are acidic, basic and amphoteric respectively.
The correct order of their electro negativity is

  Electronegativity ∝ non-metallic character.

As the element x forms acidic oxide so it is a non-metal and element forms basic oxide so it is a metal. Thus, the order of electronegativity X>Z>Y.

Hence,  correct option is (C).