Answer: D. There is one atom of sulfur and three atoms of oxygen.
Explanation:
An atom is smallest unit of a matter or substance.It consist of three subatomic particles : electrons, protons, neutrons.
Element is a pure substance which is composed of atoms of similar elements. Example: Gold

Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass. Example: water

1 molecule of
is made up of one atom of sulfur and three oxygen atoms combined together in fixed ratio by mass.