The base used in making antacids is

The development of acids in the stomach that cause acidity is known as acid reflux. They result in stomach burning and could possibly cause inflammation. Since they are acids, bases can neutralize them by forming neutralization reactions with acids.
Since water and salt are produced as byproducts of neutralization processes, our bodies are not harmed in any way. So, for the treatment, we use bases. Antacids are a type of base. They neutralize the gastric acids.

Antacids are the bases that are used to treat the acidity of the stomach. As a base neutralizes the acid to produce a neutral solution (salt + water), thus to combat the excess acid produced in the stomach, a base is taken.

Generally, antacids are composed of bases like magnesium hydroxide or sodium hydrogen carbonate.

Hence, the correct option is C.