Question

which of these is a polymer?
a single carbon atom
a strand of dna

Explanation:

A polymer is a large molecule made of repeating subunits (monomers). A single carbon atom is just an atom, not a polymer. DNA is a polymer where the monomers are nucleotides, and a strand of DNA consists of many nucleotide units linked together. So a strand of DNA is a polymer.

Answer:

a strand of DNA