What type of artwork is depicted on the cave walls according to the passage?

The correct answer, paintings, refers to the type of artwork often created using natural pigments that were applied to surfaces such as cave walls. The art found in caves, especially those from prehistoric times, typically involves the use of simple brushes made from hair or sticks, and the pigments were usually derived from minerals and other natural materials. These paintings often portray animals, human figures, or abstract symbols and are significant for providing insights into the lives and beliefs of ancient peoples. The term "murals" generally applies to large scale paintings directly on walls, which is a separate category from cave paintings as they were not applied with an architectural intent. Mosaics involve assembling small colored tiles to create images or patterns, which does not align with the nature of cave artwork. Sculptures involve three-dimensional work and are not represented in the tradition of cave wall paintings. Thus, the designation of paintings captures the essence of the artistic expressions found in cave systems.