In both DNA and RNA, heterocyclic base and phosphate ester linkages are at:

1. A
   $C_{5^{\prime }}$ and $C_{2^{\prime }}$ respectively of the sugar molecule
2. B
   $C_{2^{\prime }}$ and $C_{5^{\prime }}$ respectively of the sugar molecule
3. C
   $C_{1^{\prime }}$ and $C_{5^{\prime }}$ respectively of the sugar molecule
4. D
   $C_{5^{\prime }}$ and $C_{1^{\prime }}$ respectively of the sugar molecule