The correct option is C Milk of Magnesia
Indigestion is caused when the amount of hydrochloric acid in the stomach increases. So to counter the increase in the amount of acid we should intake a base. Among the given options oranges contain citric acid, vinegar contains acetic acid, tea contains tannic acid and milk of magnesia contains magnesium hydroxide (a base). So, to neutralise the effect of indigestion Himanshu should take milk of magnesia.