Which compound is the most soluble in water

Explanation:

Among given compounds,  ethylene glycol is the most soluble in water.
Ethylene glycol has two hydroxy groups both of which form hydrogen bonds with water.
Greater is the number of hydrogen bonds, greater is the extent of hydrogen bonding and greater is the solubility in water.

Final Answer:

Ethylene glycol is the most soluble in water.  Hence the correct option is D.