DNA and RNA are two types of nucleic acids found in living cells. Both DNA and RNA share some similarities in their structure and function. One of the similarities between DNA and RNA is that both are polymers of nucleotides.

Polymers of Nucleotides:
- Both DNA and RNA are made up of nucleotides.
- Nucleotides are monomers that are linked together to form a polymer.
- A nucleotide consists of three components: a nitrogenous base, a sugar molecule, and a phosphate group.
- The nitrogenous bases in DNA are adenine, guanine, cytosine, and thymine, while in RNA they are adenine, guanine, cytosine, and uracil.
- The sugar molecule in DNA is deoxyribose, while in RNA it is ribose.
- The phosphate group is the same in both DNA and RNA.

Replication:
- Another similarity between DNA and RNA is that both are capable of replication.
- DNA replication occurs during cell division, where a copy of the DNA is made for each daughter cell.
- RNA replication occurs during transcription, where a copy of DNA is made into RNA.

Different Sugars:
- Although both DNA and RNA are polymers of nucleotides, they have different sugar molecules.
- DNA has deoxyribose sugar, which lacks an oxygen atom at the 2' position of the ribose sugar.
- RNA has ribose sugar, which has a hydroxyl group at the 2' position of the ribose sugar.

Different Pyrimidine Bases:
- DNA and RNA have different pyrimidine bases.
- DNA has thymine as a pyrimidine base, while RNA has uracil as a pyrimidine base.
- Both DNA and RNA have cytosine as a pyrimidine base.

In conclusion, the correct answer is option 'A', which states that one of the similarities between DNA and RNA is that both are polymers of nucleotides.

Optionn A is correct