CUSO4 is an example of A COMPOUND.
A compound is the product formed when two or more elements chemically combine together to form a new product or products, which are quite different from the reactants. The elements in the compound are usually combined together in a specific ratio. In the question given above, CUSO4 is a compound because, copper, sulphur and oxgyen had combined together chemically to form a new compound, which is CUSO4. The ratio of combination is 1:1:4, that is, one atom of copper combine with one atom of sulphur and four atoms of oxygen to form one molecule of CUSO4.