What should be at the place of $A$ and $B$ in the following reaction:
$A \xrightarrow{\text{Nucleases}} B$

• A

  $A$. Nucleotides

  Nucleosides

• B

  $B$. Nucleic acids

  Nucleotides

• C

  $C$. Nucleosides

  $N$-bases + Pentose sugar

• D

  $D$. Canola

  Tobacco