Stinging hair of nettle leaves inject which of the following acid that causes burning pain?

Methanoic acid

The correct answer is option 3. Methanoic acid.

Stinging nettles (scientifically known as Urtica dioica) are plants equipped with tiny hollow hairs on their leaves and stems. These hairs contain a mixture of chemicals, including histamines, serotonin, acetylcholine, and various acids.

One of the key chemicals found in stinging hairs is methanoic acid, also known as formic acid. When the hollow hairs come into contact with the skin, they break easily, and the chemicals contained within are released. Methanoic acid, in particular, is responsible for the burning sensation and pain experienced upon contact with stinging nettles.

Methanoic acid acts as an irritant to the skin, causing inflammation and discomfort. It stimulates pain receptors in the skin, triggering a painful burning sensation. Additionally, it can induce an allergic reaction in some individuals, leading to further inflammation and discomfort.

Overall, the methanoic acid present in the stinging hairs of nettle leaves is the primary compound responsible for causing the characteristic burning pain experienced upon contact with stinging nettles.