In the DNA molecules

• Correct answer
  A

  There are two strands which run antiparallel-one in $5^{\prime} \rightarrow 3^{\prime}$ direction and other in $3^{\prime} \rightarrow$ $5+$
• B

  The total amount of purine nucleotides and pyrimidine nucleotides is not always equal
• C

  There are two strands which run parallel in the $5^{\prime} \rightarrow 3^{\prime}$ direction
• D

  The proportion of Adenine in relation to thymine varies with the organism

Hence, the correct answer is option: 'A'.