Answer:
Sulphur oxide
Step-by-step explanation:
All of the above oxides with the exception of sulphur oxide are basic oxides and so will not turn blue litmus paper red when dissolved in water. Sulphur oxide, SO2 on the other hand, is an acid anhydride (a non-metallic oxide which dissolves in water to produce acid) rendering it the ability of turning blue litmus paper red when dissolved in water.