Nylon-$6,6$ is a condensation polymer of two monomers $X$ and $Y$. The number of $-CH_2-$ groups in $X$ and $Y$ are respectively

$A$ 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.

Identify the thermosetting polymer from the following.

The polydispersity index of a polymer containing $10$ molecules with molecular mass $1.0 \times 10^4$ and $10$ molecules with molecular mass $1.0 \times 10^5$ is approximately.

Which of the following statements is incorrect?

Which of the following is $NOT$ true for polymers?