Avery did not observe transformation using the extracts containing degraded DNA. On the other hand, extracts with degraded RNA, proteins, and polysaccharides exhibited transformation. Therefore, he concluded that DNA is the genetic material responsible for transformation. If he would have observed the process of transformation using extracts containing degraded DNA but not with degraded polysaccharides, he might have concluded that "polysaccharides were the genetic material responsible for the process of transformation."
Sophie is wrong because although dolphins and sharks can technically be said to be similar, it resulted from convergent evolution, which has nothing to do with common ancestry and rather to do with similar environments for their homes.