Terylene is the polyester of

If a plastic is hard,which substance is added to it to introduce the property of softness?

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?

Match $List-I$ with $List-II$.

$List-I$ (Polymer)	$List-II$ (Monomer)
$(A)$ Neoprene	$(I)$ Acrylonitrile
$(B)$ Teflon	$(II)$ Chloroprene
$(C)$ Acrilan	$(III)$ Tetrafluoroethene
$(D)$ Natural rubber	$(IV)$ Isoprene

Choose the correct answer from the options given below.

Which of the following polymers contains nitrogen?

If the number average molecular weight and weight average molecular weight of a polymer are $40000$ and $60000$ respectively, the polydispersity index of the polymer will be