Which of the following is a step-growth polymer?

Which of the following is an example of a chain-growth polymer?

The expected reactivity of the monomers shown below towards cationic polymerization follows the order:
$I: CH_2=CH-CO_2CH_3$
$II: CH_2=CH-Cl$
$III: CH_2=CH-CH_3$
$IV: CH_2=CH-Ph$

The catalyst used in the manufacture of high-density polyethylene is:

Ziegler-Natta catalyst is used for which type of reaction?

Bakelite is obtained from phenol by reacting with