The Magnitude of the Union-Non-Union Wage Differential Depends on All

The magnitude of the union-non-union wage differential depends on all of the following, except:

A) the elasticity of labour demand in each sector.
B) the substitutability between two sectors of workers in the same industry.
C) the ability of the union to raise wages in the organized sector.
D) the elasticity of labour supply in the non-union sector.
E) the size of the union sector relative to the non-union sector.