What is the monomer of natural rubber?

Which monomer is present in bakelite?

$(i)$ Give one example with a chemical equation for the following reactions:
$(a)$ Substitution reaction.
$(b)$ Saponification reaction.
$(c)$ Combustion reaction.

Which of the following is a natural polymer?

Which of the following is not a biopolymer?

Explain the given reactions with examples:
$(a)$ Saponification reaction
$(b)$ Combustion reaction