Which one of the following is not applicable for RNA?

RNA is single stranded, so it doesn't follow Chargaff's rule. Chargaff's rule states that DNA from any cell of all organisms should have a 1:1 ratio (base Pair Rule) of pyrimidine and purine bases, that the amount of guanine (G) is equal to cytosine (C) and the amount of adenine (A) is equal to thymine (T). Thus, the correct answer is option A.