Modified natural plastics include which of the following?

Modified natural plastics refer to materials that have been derived from natural sources but have undergone modifications to enhance their properties and performance for specific applications.

Cellulose and casein fall into this category because they are both derived from natural substances. Cellulose is a polysaccharide found in the cell walls of plants, while casein is a protein derived from milk. Both materials can be processed and modified to create various types of plastics that maintain some of the properties of their natural origins while improving factors like durability, flexibility, and usability in manufacturing.

The other options listed, such as Polyvinyl Chloride (PVC), Polystyrene, and Acrylics, are synthetic plastics. These materials are created from petrochemical sources through polymerization processes and do not have the natural origins that modified natural plastics do. Therefore, they do not fit the criterion of being modified natural plastics.