Final answer:
If Avery, MacLeod, and McCarty had found that proteases stopped the transformation, it would indicate that proteins were responsible for the transformation of R strain bacteria. However, their actual experiment showed that only when DNA was degraded was the transformation inhibited, establishing DNA as the transforming principle.
Step-by-step explanation:
If the groundbreaking experiments by Avery, MacLeod, and McCarty had revealed that the transforming molecule was a protein, different experimental results would have been observed. Specifically, if proteases (enzymes that degrade proteins) had prevented the transformation of R strain bacteria, it would imply that proteins were the critical molecule for the transformation process. Consequently, this would mean that in the presence of proteases, transformation would not have been observed (Answer A), as the necessary proteins would have been degraded, unable to carry out the transformation of R strain into S strain. However, their actual experiment showed that the transformation was inhibited only when DNA was destroyed, leading to the conclusion that DNA was the transforming principle, not proteins.