Answer: Both are composed of nucleotides
Explanation:
Both DNA and RNA are common in that they are composed of nucleotides of Adenine, Guanine, Cytosine.
However, they are not composed of the same nucleotides, because nucleotides of thymine is found only in DNA, while nucleotides of uracil is found only in RNA.
Thus, RNA and DNA are common because they are composed of nucleotides of nitrogenous bases