Question

Which substance can be decomposed by a chemical change?

Answer 1

The answer to this question would be: ammonia
Chemical decomposition is the breakdown of a compound into smaller compound or element. In this question, the Sodium(Na), Argon (Ar) and Sulfur(S) is elements, not compounds.
An element should not breakable since it was the simplest form.
Ammonia(NH3) is a compound so it should be able to be decomposed.