Case: Read the passage and answer the following questions

There are two broad types of polymerization reactions, i.e., the addition or chain growth polymerization and condensation or step growth polymerization. In the addition polymerization, the molecules of the same monomer or different monomers add together on a large scale to form a polymer. The monomers used are unsaturated compounds, e.g., alkenes, alkadienes and their derivatives. This mode of polymerization leads to an increase in chain length and chain growth can take place through the formation of either free radicals or ionic species while condensation polymerization generally involves a repetitive condensation reaction between two bi-functional or tri-functional monomeric units. These poly-condensation reactions may result in the loss of some simple molecules as water, alcohol, hydrogen chloride, etc. and lead to the formation of high molecular mass condensation polymers.
In these reactions, the product of each step is again a bi-functional species and the sequence of condensation goes on. Since, each step produces a distinct functionalized species and is independent of each other, this process is also called step growth polymerization.

Which method is used to prepare co-polymers?

Both of the above

The co-polymer can be made not only by chain growth polymerisation but by step growth polymerisation also. It contains multiple units of each monomer used in the same polymeric chain.