Final answer:
The force that pushes materials together is called compression, and it involves the internal forces within a material that can be attractive, leading to the material being compressed.
Step-by-step explanation:
A force that pushes materials together is known as compression. When internal forces within an object are attractive, they can cause materials to be pushed or pulled together, which could result in the compression of the material. This is a type of energy interaction, where the internal force is the simple particles that make up an extended object exerting force on each other. The magnitude of compression is related to the force exerted per unit area and the original volume of the object, which together determine how much an object can compress, depending on the compressibility of the substance.
Answering the student's question: a force that pushes materials together would best be described as b.) compression.