At standard pressure, a certain compound has a low boiling point and is insoluble in water. at stp, this compound most likely exists as
(1) ionic crystals
(2) metallic crystals
(3) nonpolar molecules
(4) polar molecules

Answer is (3) - nonpolar molecules.

Nonpolar molecules make weak attractions between molecules called van der Waals forces. Hence, they are looesly bound with each other. Therefore, nonpolar molecules can easily go to the atmosphere by breaking those weak bonds. Hence, the boiling point is low.

Since water is a polar solvent, nonpolar molecules do not soluble in water.

- lead + phosphoric acid = hydrogen + lead(ii) phosphate