Which of the following statements is correct regarding the $DNA$ molecule?

• A
  The ratio of $Adenine$ to $Thymine$ varies significantly among different organisms.
• B
  It consists of two strands that run antiparallel,one in the $5' \rightarrow 3'$ direction and the other in the $3' \rightarrow 5'$ direction.
• C
  The total amount of $Purine$ and $Pyrimidine$ nucleotides is always equal.
• D
  It consists of two strands that run parallel in the $5' \rightarrow 3'$ direction.