At which position does the phosphate group attach to the pentose sugar in a nucleotide?

$DNA$ sequences that code for proteins are known as:

The backbone of the $DNA$ molecule is composed of which of the following?

How many nucleotide pairs are present in one full turn of the $DNA$ helix?

Choose the incorrect statement.

Identify the correct matching for Euchromatin and Heterochromatin from the given statements:
$I -$ Loosely packed
$II -$ Densely packed
$III -$ Darkly stained region
$IV -$ Lightly stained region
$V -$ Transcriptionally active chromatin
$VI -$ Transcriptionally inactive chromatin
Euchromatin $\quad\quad$ Heterochromatin