Ebonite is:
A) Polypropene
B) Natural rubber
C) Synthetic rubber
D) Highly vulcanized rubber

Hint: The material ebonite is known as a branded name which is generally known as hard rubber. It contains sulfur as its ingredient and one can relate this data to the given options and sulfur can be used for only one type of rubber and choose the correct option.

Complete step by step answer:
1) First of all we will learn about the ebonite material. The ebonite is a hard rubber that is obtained by processing the natural rubber material.
2) The name of ebonite is used due to its intended use as an artificial substitute for ebony wood. The ebonite material may consist of ${\text{25% }}$ to ${\text{80% }}$ of sulfur and linseed oil as its constituents.
3) The percentage of sulfur and the temperature which is applied for the conversion of the natural rubber to ebonite determine the technical properties of the hard rubber formed.
4) The reaction during this process is simply an addition of sulfur to the double bonds which form the intramolecular ring structures. This makes the structure a highly cross-linked structure that has an intramolecular addition reaction.
5) The maximum addition of sulfur can be up to ${\text{40 % }}$ which makes the rubber resistant to swelling and to minimize the dielectric loss. This addition of sulfur in natural rubber is called a vulcanization process.
Therefore, Ebonite is a highly vulcanized rubber which shows option D as the correct choice.


Note: Ebonite is the material which is obtained by processing the natural rubber for such a long period with sulfur and high temperature. This results in the formation of very firm vulcanized rubber i.e. hard rubber and low-elastic. Ebonite has a very less elongation percentage which is approximately ${\text{ 3% }}$ only.