**False Statement:**
b) Nylon-66 is an example of elastomer.

**Explanation:**
To determine the false statement among the given options, let's analyze each statement one by one:

a) Artificial silk is derived from cellulose.
- This statement is true. Artificial silk, also known as rayon or viscose, is derived from cellulose. Cellulose is a natural polymer found in the cell walls of plants and is the main component of wood and cotton. It is chemically processed to obtain a viscous solution, which is then extruded into fibers to create artificial silk.

b) Nylon-66 is an example of elastomer.
- This statement is false. Nylon-66 is a type of synthetic polymer known as a polyamide. It is formed by the condensation polymerization of adipic acid and hexamethylenediamine. Nylon-66 is a strong and durable material with high tensile strength and heat resistance, making it suitable for various applications such as textiles, engineering plastics, and automotive parts. However, it is not an elastomer.

c) The repeat unit in natural rubber is isoprene.
- This statement is true. Natural rubber is a polymer of isoprene. Isoprene, also known as 2-methyl-1,3-butadiene, is a monomer that polymerizes to form natural rubber. The repeat unit of natural rubber is composed of five carbon atoms and has a branched structure.

d) Both starch and cellulose are polymers of glucose.
- This statement is true. Both starch and cellulose are polysaccharides composed of glucose monomers. Starch is a carbohydrate polymer found in plants and serves as a storage form of energy. It consists of two components: amylose, which is a linear chain of glucose molecules, and amylopectin, which is a branched chain of glucose molecules. On the other hand, cellulose is the main structural component of plant cell walls. It forms long, linear chains of glucose molecules connected by β-1,4 glycosidic bonds.

Therefore, the false statement among the given options is b) Nylon-66 is an example of elastomer.