Which of the following statements are correct with reference to the packaging of the $DNA$ helix?

• A
  $A$. Histones are organized to form a unit of eight molecules called a histone octamer.
• B
  $B$. Histones are negatively charged basic proteins.
• C
  $C$. Histones are rich in the basic amino acid residues - lysine and arginine.
• D
  $D$. The positively charged $DNA$ is wrapped around the histone octamer to form a nucleosome. $E$. The packaging of chromatin at higher levels requires an additional set of proteins called non-histone chromosomal proteins.