Which $N_2$ base is absent in the structure of $RNA$?

Which sugar is found in $RNA$?

The functional unit of mutation is

Which of the following statements is inconsistent with $DNA$?

In the structure of $DNA$,if a purine base is present on one nucleotide strand,which nitrogenous base pairs with it?

If the distance between two consecutive base pairs in a $DNA$ molecule is $0.34 \ nm$ and the total number of base pairs in a typical mammalian cell is $6.6 \times 10^9 \ bp$,what is the approximate length of the $DNA$ (in $m$)?