. . . . . . . . is an example of monoatomic molecule. A. Argon B. Sulphur C. Phosphorus D. Hydrogen

The correct answer is: Argon (A).

A monoatomic molecule is a molecule that consists of only one atom. Argon is an example of a monoatomic molecule because it is a noble gas that exists as a single atom at standard temperature and pressure. The other options are not monoatomic molecules because they are made up of multiple atoms.

Sulphur (B) is a non-metal that exists as a molecule with eight atoms. Phosphorus (C) is a non-metal that exists as a molecule with four atoms. Hydrogen (D) is a gas that exists as a molecule with two atoms.