What did Chargaff discover while studying bases in the DNA of organisms

A.The bases in the DNA of each organism were unique.
B.The ratios of thymine and adenine were similar, as were the ratios of guanine and cytosine.
C.The overall percentages of bases were different from one organism to the next.
D.There were equal amounts of all four bases in every organism, or 25 percent of each base.