Solution

A monomer is a molecule that forms the basic unit for polymers.

A polymer is a chemical compound with molecules bonded together in long, repeating chains.

Isomers are two or more compounds with the same formula but a different arrangement of atoms in the molecule and different properties.

Equimers are two isomers with different configurations of atoms about one or several asymmetric carbon atoms present.

The name of $$CH_2=CH_2$$ is ethylene, which is a single molecule so can't be a polymer, isomer, or equimer. This is the monomer of polyethylene.

Hence, option $$A$$ is correct.