Answer 1

 Methanoic acid is injected into the skin during a nettle-leaf-hair sting

 a nettle-leaf-hair sting are acidic, as methanoic acid is injected into the body, which causes severe pain and an itching sensation. Applying a baking soda solution (a base) on the skin soothes the pain by neutralising the acid. Thus, the effect of these stings is neutralised.