Which of the following statements forms the basis of $DNA$ fingerprinting?

• A
  The relative proportions of purines and pyrimidines in $DNA$.
• B
  Satellite $DNA$ occurring as highly repeated short $DNA$ segments.
• C
  The relative difference in the $DNA$ occurrence in blood,skin and saliva.
• D
  The relative amount of $DNA$ in the ridges and grooves of the fingerprints.