Answer : The compound that would be most soluble in water is CH3CH2CH2OH
Explanation :
Water is a polar solvent and can dissolve polar molecules. This is based on the principle "Like dissolves like".
Among the given molecules, CH3CH2CH2CH3 is a hydrocarbon known as butane. All hydrocarbons are non polar. Therefore this compound will not be soluble in water.
The remaining compounds are polar, but Ch3CH2CH2OH shows greater solubility in water owing to presence of hydrogen bonding.
Hydrogen bonding is a type of intermolecular force that gets formed when a compound has hydrogen atom directly attached to highly electro-negative N, F or O atom.
When CH3CH2CH2OH is dissolved in water, it forms hydrogen bonds with water molecules. Due to this hydrogen bonding, the molecule shows greater solubility.
Therefore CH3CH2CH2OH is the most soluble compound in water