Which of the following is not a pyrimidine?

The function of $DNA$ in an organism is

Identify the set containing purine and pyrimidine base of $DNA$ respectively.

In both $DNA$ and $RNA$,the heterocyclic base and phosphate ester linkage are present at which positions of the sugar respectively?

In a nucleotide,the phosphate linkage is generally attached to -

What are the positions of $N$ atoms present in the pyrimidine ring of nucleic acids?