According to Chargaff's rules, which of the following statements is true about the composition of double-stranded DNA?

• A. The amount of purines is equal to the amount of pyrimidines.
• B. The amount of adenine is equal to the amount of guanine.
• C. The amount of adenine is equal to the amount of cytosine.
• D. The amount of cytosine is equal to the amount of thymine.

Answer: (A)