Oil of clove, also called clove oil, is a powerful essential oil obtained from the clove plant. It is known for its antiseptic properties and its warming, stimulating effect when used in aromatherapy. The primary active component of oil of clove is eugenol, which makes up about 70-85% of the oil.

Option 1, menthol, is incorrect because it is the main component in peppermint oil, not clove oil.

Option 3, methanol, is also incorrect. Methanol is an alcohol, not a constituent of clove oil.

Option 4, benzaldehyde, is part of bitter almond oil and not found in clove oil.

So, option 2, Eugenol, is the correct answer as it is the main ingredient in oil of clove.