Definition check: a copolymer is formed by the chemical combination of two or more different monomer species. Which option best matches this idea in simple exam convention?

Introduction / Context:
In elementary polymer chemistry exams, “copolymer” commonly refers to addition copolymers such as SBR (styrene–butadiene rubber) or ABS (acrylonitrile–butadiene–styrene). While copolymers can also be made by condensation, many question banks emphasise the simple addition model to test monomer identity recognition.

Given Data / Assumptions:

• The prompt asks for the best match “in simple exam convention”.
• Options distinguish addition versus condensation and same versus different monomers.

Concept / Approach:
A copolymer requires at least two different monomer types incorporated into one macromolecular chain. In many standard MCQs, the default mental model is addition polymerisation of vinyl monomers without elimination of small molecules. Therefore, the option that explicitly states “without the elimination of water” and involves chaining monomers fits the expected exam framing.

Step-by-Step Solution:
Identify options that involve two different monomers.Select the addition-type description as the conventional answer.Note that more advanced courses accept condensation copolymers too, but the question’s framing points to the addition view.

Verification / Alternative check:
Common examples of addition copolymers in textbooks include SBR, SAN, ABS; they involve no elimination of water or alcohol during chain growth.

Why Other Options Are Wrong:
(b) Describes condensation (can form copolymers, but the exam convention here leans to addition).(c) Same monomer → homopolymer, not copolymer.(d) Invalid because a suitable description exists.

Common Pitfalls:
Over-generalising: in reality, copolymers may form via condensation; however, follow the exam’s intended emphasis unless stated otherwise.

Final Answer:
In a chain without the elimination of water (addition route).