Answer
a.
Work Step by Step
Chargaff found that percentages of certain bases are almost always equal in any sample of DNA. For example, he found that the percentages of adenine and thymine were almost equal and the percentages of cytosine and guanine were almost identical. This discovery led to Chargaff's rule, which stated that adenine always paired with thymine whereas cytosine always paired up with guanine.
