An eager grad student attempted the famous Meselson and Stahl experiment with a twist. She first grew E. coli in media containing 'light' 14N isotopes which the bacteria incorporated into their DNA. She then switched to 'heavy' media containing 15N isotopes and grew the bacteria for 2 generations. She then switched back to media containing 14N isotopes and grew the bacteria for 1 more generation. She isolated the DNA and analyzed the molar ratios of 15N:15N DNA, 15N:14N hybrid DNA, and 14N:14N DNA by centrifugation. Assuming semi-conservative replication, the expected molar ratios are: Group of answer choices