Which of the following alkanes has the highest boiling point?

The boiling point of a compound depends on the strength of the intermolecular forces between its molecules. The stronger the intermolecular forces, the higher the boiling point. In this case, all of the given alkanes are nonpolar molecules and have only weak London dispersion forces between their molecules. Therefore, the boiling point of these alkanes increases with increasing molecular weight (number of carbon atoms). Out of the given alkanes, pentane has the highest molecular weight and therefore, it has the highest boiling point. Hence, the answer is pentane.