(a) We take an antacid such as milk of magnesia to neutralizes the excessive acid released in the stomach.
(b) Ant injects an acidic liquid (Formic acid) into the skin on biting which causes inflammation, to the skin. The effect of the acid can be neutralized by rubbing. Calamine solution contains zinc carbonate which is a very weak base and causes no harm to the skin.
(c) The wastes of factories contain acids. If acids are disposed of in the water body, the acids will harm the organisms. So factory wastes are neutralized by adding basic substances.