Step 1: Understanding the Concept:
There are several standard ways to classify polymers.
Step 2: Detailed Explanation:
Source: natural, semi-synthetic, synthetic. Structure: linear, branched, cross-linked. Mode of polymerisation: addition or condensation. Molecular forces: elastomers, fibres, thermoplastics, thermosetting.
The "number of monomers" in a chain is not a standard classification basis. Homopolymer versus copolymer depends on the type of monomers, not on how many units there are.
Step 3: Final Answer:
Option (B) is not a basis.
Final Answer:
Number of monomers is not a classification basis.
\[ \boxed{\text{(B) }\text{Number of monomers}} \]