The correct answer is option 3: Antacid. Antacids are a type of medicine that is commonly used to treat indigestion. Indigestion is a condition characterized by discomfort or pain in the upper abdomen, often caused by excess stomach acid. Antacids work by neutralizing the acid in the stomach, which helps to relieve symptoms such as heartburn, bloating, and stomach discomfort.

Option 1: Antibiotics are not used for treating indigestion. Antibiotics are medications that are used to treat bacterial infections, not digestive issues.

Option 2: Analgesics are a type of medicine used primarily for pain relief. While they may provide temporary relief for some symptoms associated with indigestion, such as stomach pain, they do not directly treat the underlying cause of indigestion.

Option 4: Antiseptics are used to kill or inhibit the growth of microorganisms on the skin or in wounds. They are not used for treating indigestion.

Therefore, the correct answer is option 3: Antacid.