Answer: B. but the relative amounts of G+C and A+T vary by species.
Explanation: Chargaff's rule states a relantionship between guanine (G) and cytosinev(C) amounts and adenine (A) and thymine amounts (T). But these amounts could change across species, so much so, GC content is a characteristic of each species genome. For example, there some bacteria like Actinobacteria classified as " high GC bacteria", a plant Arabidopsis thaliana has 36% of GC content and others like Plasmodium sp. are classified as "high AT content".
