Concept:The boiling point depends on the strength of intermolecular forces. Stronger forces require more heat energy to separate the molecules.Explanation:Butane, C4H10, is a non-polar alkane. It has only weak van der Waals forces between its molecules.Ethanoic acid, CH3COOH, water, H2O, and ethanol, C2H5OH, can form hydrogen bonds.Hydrogen bonds are much stronger than van der Waals forces, so these compounds boil at higher temperatures.Approximate boiling points are:Butane: −1∘CEthanol: 78∘CWater: 100∘CEthanoic acid: 118∘CSince butane has the weakest intermolecular forces, it boils at the lowest temperature.Answer:A. C4H10 (butane)