In which option are the substances correctly classified?

Elements, compounds, and mixtures are the three categories into which the material can be divided. Pure substances are elements. Compounds are a combination of elements in a specific ratio, whereas mixtures are impure entities made up of elements blended in any composition.

Substances created from a single type of atom are known as elements. An element cannot be converted into another substance in any way. These serve as the fundamental building blocks from which the cosmos is constructed. Carbon, sulphur, oxygen, iron, copper, and aluminium are a few examples. 

Atoms of various elements are joined by chemical bonds to form compounds, which are then substances. A chemical reaction can break down a substance into its component parts. Water $\left({\mathrm{H}}_2\mathrm{O}\right)$, sodium chloride $\left(\mathrm{NaCl}\right)$, and methane $\left({\mathrm{CH}}_4\right)$ are typical examples.

A simple combining of elements or compounds creates a mixture. There are no new chemical bonds created. Physical methods such as filtration, chromatography, evaporation, magnetization, flotation, and distillation can be used to separate mixtures. An alloy made of many metals, such as bronze and brass, are examples of mixture.

In the given options, sulfur is a pure element and water formed from hydrogen and oxygen is a compound and brass is a mixture (alloy) of copper and zinc.

Hence, the correct answer is option B.