Which of the following polymers is used to manufacture articles like raincoats?

The polymer $\begin{array}{*{20}{c}} {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,CH_3\,\,\,\,\,\,\,\,\,\,\,\,\,CH_3} \\ {\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|} \\ {{( - CH_2 - C - CH_2 - C - )}_n} \\ {\,\,\,\,\,\,\,\,\,\,\,\,|\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,|} \\ {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,CH_3\,\,\,\,\,\,\,\,\,\,\,\,\,CH_3} \\ \end{array}$ is formed from which monomer unit?

Which of the following polymers does not contain an $N$ atom?

Which of the following polymers contains an ester linkage?

Which one of the following is an example of thermosetting polymers?

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?