Identify the monomer of the given polymer structure.

Urea formaldehyde resin is an example of

Which of the following polymers is used in the controlled release of drugs?

Natural rubber is a polymer of ....

$A$ natural linear polymer of $2-$methyl$-1,3-$butadiene becomes hard on treatment with sulphur between $373 \ K$ to $415 \ K$ and $-S-S-$ bonds are formed between chains. Write the structure of the product of this treatment.

Phenol and formaldehyde undergo condensation to give a polymer $(A)$ which on heating with formaldehyde gives a thermosetting polymer $(B)$. Name the polymers. Write the reactions involved in the formation of $(A)$. What is the structural difference between the two polymers?