What is the full form of $NHC$?

Which one of the following can form a nucleotide of $DNA$?

The modern concept of gene is

$S$ Statement: $DNA$ is inherited by organisms produced by parents.
$R$ Reason: $DNA$ acts as a gene.
$(a)$ Both $S$ and $R$ are true,and $R$ is the correct explanation of $S$.
$(b)$ Both $S$ and $R$ are true,but $R$ is not the correct explanation of $S$.
$(c)$ $S$ is true and $R$ is false.
$(d)$ $S$ is false and $R$ is true.
$(e)$ Both $S$ and $R$ are false.

In the structure of a dinucleotide,between which carbons of the sugars of two consecutive nucleotides is the phosphodiester bond formed?

What is the unit formed by eight molecules of histone called?