Answer :Option (a) is the correct answer.
When atoms which are chemically combine to each other through sharing of electrons, that is, forming covalent bonds with each other then the compound formed is known as a molecular compound.
For example, is a molecular compound.
Generally, non-metals lead to the formation of molecular compounds.
On the other hand, when an electron is transferred from one atom to another then compound formed is known as ionic compound.
For example, is an ionic compound.
Generally, metals and no-metals on chemically combining together leads to the formation of ionic compounds.
Thus, we can conclude that sulfur, fluorine is the pair of elements which is most apt to form a molecular compound with each other.