First, remember that:
The vapor pressure of a liquid is directly related to the intermolecular forces present between its molecules. If these forces are stronger, the evaporation rate and the vapor pressure will be lower.
So, we're going to analyze the intermolecular forces of each element:
O2: The molecule of oxygen consist of two oxygen atoms bonded together by a double bond. It consist of just London dispersion forces, so this is a really weak force.
H2O: Water has hydrogen bonds, dipole-induced dipole forces, and London dispersion forces. So it has strong forces.
SO: It consists of London dispersion forces, and there's a difference of electronegativity between S and O, so there's a greater force than the force of O2.
Therefore, O2 could have the highest vapor pressure, as its intermolecular forces are the weakest.