Final answer:
The conclusion the scientists would have drawn is that DNA is the transforming principle.
Step-by-step explanation:
The conclusion the scientists Avery, MacLeod, and McCarty would have drawn if the use of proteases prevented the transformation of R strain bacteria is that DNA is the transforming principle.
In their experiments, they found that when the DNA was degraded, the resulting mixture was no longer able to transform the bacteria, whereas the samples treated with protease did not prevent the transformation. This led them to conclude that DNA was the transforming principle.