Chargaff's Rules State That

Chargaff's rules state that:

A) The amount of guanine plus cytosine in mammalian genomes varies from about 39 to 46%.
B) DNA is always double stranded and RNA is always single stranded.
C) DNA contains two grooves,a major groove and a minor groove.
D) In DNA the number of adenine residues is identical to the number of thymine residues and the number of guanine residues is identical to the number of cytosine residues.
E) DNA contains two strands that run in opposite directions.