Which substance is not present in nucleic acid?

Which of the following is not a pyrimidine?

Given below are two statements:
Statement $I$: $A$ unit formed by the attachment of a base to $1'-$position of sugar is known as nucleoside.
Statement $II$: When nucleoside is linked to phosphorous acid at $5'-$position of sugar moiety,we get nucleotide.
In the light of the above statements,choose the correct answer from the options given below:

The function of $DNA$ in an organism is

Which of the following bases is bicyclic?

Which one is not a constituent of nucleic acid?