Statement - I : Solid angle is a dimensionless quantity and it is a supplementary quantity
Statement - II :All supplementary quantities are dimensionless

Throughout the International economy, dimensionless units have been combined alongside base units just to generate derived units are known as supplementary quantities.

Supplementary quantities are of two types, such as:

Plane angle - radian (rad)
Solid angle - steradian (sr)

These are not having dimensions but has units.