Answer: Heterogeneous
Step-by-step explanation: Element is a pure substance which is composed of atoms of similar elements. Example:

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

Mixtures are heterogeneous materials as they do not have uniform composition and the components are not evenly distributed throughout the material and there is a distinct boundary. Example: Sand in water
Homogeneous mixtures are those in which components are evenly distributed throughout the material and thus there is no distinct boundary.Example: Milk in water