Explanation

A) Hydrogen - Very low solubility in water, decreases with increasing temperature.

B) Oxygen - Solubility decreases with increasing temperature; however, it is more soluble than hydrogen.

C) Air - A mixture of gases (mostly nitrogen and oxygen); individual gases like oxygen can dissolve, but overall solubility is affected by temperature.

Correct Answer: B) Oxygen

Oxygen is more soluble in water than hydrogen, and although its solubility decreases with increasing temperature, it remains the most soluble option among those listed.