Since the chromatic number is always equal or greater than the clique number, the chromatic number of the visibility graph of sets in A is also unbounded.

Cibulka, Kyncl and Valtr have also indirectly solved problem 2.

## Problem 2 solved

Since the chromatic number is always equal or greater than the clique number, the chromatic number of the visibility graph of sets in A is also unbounded.

Cibulka, Kyncl and Valtr have also indirectly solved problem 2.