Answer : The option is, (D) Mn
Explanation :
Pure substance : It is defined as a substance that is made by the combination of only one type of atom or only one type of molecule.
Compound : It is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.
Element : It is a pure substance which is composed of atoms of similar elements.
Molecule : It is the smallest particle in the chemical compound or chemical element that has the same chemical properties of that compound or element.
Option A :
is molecule of element.
Option B :
is molecule of compound.
Option C :
is molecule of compound.
Option D :
is and element.
Hence, the element Mn is not an example of a molecule.