Final answer:
In the context of dental restorations, the matrix used for anterior composite resin or glass ionomer restorations is typically made of clear plastic. This type of matrix allows for easy shaping and light curing of the restorative material.
Step-by-step explanation:
The matrix referenced in the question is most likely referring to the type of matrix system used for anterior composite resin or glass ionomer restorations in dentistry. For these types of restorations, D) Clear Plastic matrices are commonly used. The clear plastic matrix allows the dentist to mold the restorative material to the desired shape while also being able to cure the material with a dental curing light through the transparent plastic. This is in contrast to Ceramic-matrix composites and Metal-matrix composites, which consist of reinforcing fibers embedded in a ceramic matrix or a metal/metal alloy matrix, respectively, and are used in more advanced engineering applications rather than routine dental restorations.