Here's why:

* Elements are the simplest pure substances that cannot be broken down further by chemical means. They are made up of only one type of atom.

* Mixtures are combinations of two or more substances that are not chemically bonded. They can be separated by physical means.

* Compounds are formed when two or more elements combine chemically in a fixed ratio.

Sulfur exists as a pure substance consisting only of sulfur atoms. It cannot be broken down into simpler substances, making it an element.