Choose the incorrect sentence.

• A
  $A$ typical nucleosome contains $200$ bp of $DNA$ helix.
• B
  Nucleosomes constitute the repeating unit of a structure in the nucleus called chromatin,which are thread-like stained bodies seen in the nucleus.
• C
  In a typical nucleus,some regions of chromatin are loosely packed and are referred to as heterochromatin.
• D
  Euchromatin is said to be transcriptionally active chromatin,whereas heterochromatin is inactive.