Because almost all small streams end up in bigger bodies of water.
A compound that has Carbon and Hydrogen
The answer is most likely B). 'The harmless bacteria would not have been transformed, and the mice would have lived,' because, then bacterium transform, they use the genetic material present in their environment to do so, and when Avery destroyed the nucleotide bases(Genetic material) with an enzyme he destroyed any chances that the bacteria would have had at transforming into the virulent strain.
D : the number of generations in one population