The correct option is C Antacid
Antibiotics are a type of antimicrobial used in the treatment and prevention of bacterial infection. It kills the bacteria or stops bacteria from multiplying. So there is nothing to deal with indigestion.
Analgesics are usually used to relieve severe pain.
Antacids are taken to relieve heartburn or indigestion caused by excess stomach acid. It contains alkaline ions that directly neutralize stomach gastric acid. Hence, it can be used for treating indigestion using the concept of neutralization reaction.
Antiseptic are antimicrobial substance that are applied to living tissue/skin to reduce the possibility of infection.
So, only antacid is a substance which is used for treating indigestion using the concept of neutralization reaction.