The base adenine is found in ........

Which of the following substances is not present in nucleic acids?

Identify the nitrogenous base of nucleic acid from the following that has a double-ring structure.

Which of the following is not a purine?

Uracil is a base present in $RNA$ with the following structure. The percentage of $N$ in uracil is $............$.
Given:
Molar mass $N = 14 \, g \, mol^{-1} ; O = 16 \, g \, mol^{-1} ; C = 12 \, g \, mol^{-1} ; H = 1 \, g \, mol^{-1}$.

Which of the following bases are present both in $DNA$ and $RNA$?