[单选题]
The graph below shows the results of
guh6p8 o8 rd.z/6;cfm,yt elc an experiment conducted by a tea
nui; x,1 ud +koce2vrss)mm8;m of researchers investigating the relationship between the composition and melting point of differen
s mec; 1mkn2 uor;8xud,+sv)it DNA samples. At the melting point, the DNA double helix separates into two individual strands.
Two DNA samples were compared, one consisting of only PQ pairs and another one consisting of only RS pairs. Letters P, Q, R and S represent different nitrogenous bases found in the DNA.
Based on the results presented in the graph, and your knowledge of nucleotide base pairing (between purines and pyrimidines), deduce which nitrogenous bases correspond to the letters P, Q, R and S.
