By repetitive combinations of simple subunits. Hence, option A is correct.
What are polymers?
A polymer is any of a class of natural or synthetic substances composed of very large molecules, called macromolecules, which are multiples of simpler chemical units called monomers.
Polymers are large molecules made up of long chains or networks of smaller molecules called monomers.
Natural polymers include silk, hair, proteins and DNA, while synthetic (man-made) polymers include polyethene, polypropylene and polyester.
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