Theoretically it is the Chargaff's rule which entails that the ratio of purines and pyrimidines are 1. So following that rule you can solve this question.
G (purine) = C (pyrimidine) and
A (purine) = T (pyrimidine)
So G + C would be 28% and hence
A +C would be 72% i.e. 36% each.
Please note that their are certain modified bases besides these four are also there including methyl Cytosine, Methylated Adenine. But htese modification does not violate the Chargaff's rule and they follow standard Watson Crick base pairing.
I think the best answer is letter b. which is all of these. By studying fossils, a scientist can determine what organism is found. The scientist also can determine the age of the fossil but it can be recognized as a fossil if it was older than 5,000 years. And lastly, fossils can illustrate the changes of environment, climate and evolutionary patterns of our world.
