$$ \text { Match the following : } $$

$$ \begin{array}{llrl} \hline & \text { List-I (Use) } & & \text { List-II (Substance) } \\ \hline \text { A. } & \text { Electrodes in batteries } & \text { I. } & \text { Polypropylene } \\ \hline \text { B. } & \text { Welding of metals } & \text { II. } & \text { Polyacetylene } \\ \hline \text { C. } & \text { Toys } & \text { III. } & \text { Oxyacetylene } \\ \hline \end{array} $$

The correct answer is

A polymer sample contains 10 molecules each with molecular mass 5,000 and 5 molecules each with molecular mass 50,000 . The number average molecular mass of the polymer sample is

The number of linear and crosslinked polymers in the following respectively are

Novolac, Nylon 6,6, Bakelite, PVC, melamine

Which one of the statements, regarding $X$ is not correct?

3-Hydroxybutanoic acid +3 -Hydroxypentanoic acid $\rightarrow X$