The correct option is A.
Elements are substances that are made up of atoms of the same type., while compounds are made of two or more atoms of different types.
Some common examples of elements are Iron, Sodium, oxygen, Hydrogen, while NaCl ( Sodium Chloride), Water (H_2O) , Ammonia (NH_3) are compounds.
It can be seen that the compounds are composed of atoms of different substances.
Chlorine is a diatomic molecule, where two Chlorine atoms are bonded by a covalent bond. Since both atoms in a Chlorine molecule are the same, it cannot be called a compound.
Hence Chlorine, though it has more than one atom in its molecular form, is still called element.
