(a) We take an antacid such as milk of magnesia to neutralises 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 neutralised by rubbing. Calamine solution contains zinc carbonate which is a very weak base and causes no harm to the skin.(c) The waste of factories contain acids. If acids are disposed of in the water body, the acids will harm the organisms. So factory wastes are neutralised by adding basic substances.