The correct answer to the question is option 2: Methanoic acid.

Nettle leaves have tiny hairs on their surface called trichomes, which contain chemicals such as histamine, serotonin, and formic acid. When these hairs come into contact with the skin, they inject these chemicals into the skin, causing a burning pain and irritating sensation.

Methanoic acid, also known as formic acid, is a colorless liquid that has a pungent smell. It is naturally found in the venom of certain insects, including stinging ants and bees. Methanoic acid is responsible for the burning sensation and pain experienced when stung by these insects.

It is important to note that options 1 (Acetic acid), 3 (Sulphuric acid), and 4 (Hydrochloric acid) are incorrect choices for this question. Acetic acid is the main component of vinegar and does not cause the specific burning pain associated with nettle stings. Sulphuric acid and hydrochloric acid are strong acids that can cause severe burns and tissue damage, but they are not present in nettle leaves and are not responsible for the pain caused by their stinging hairs.

In conclusion, the correct answer is option