Answer :
Answer:
a. Griffith
Explanation:
Frederick Griffith used two strains of the bacterium Streptococcus pneumoniae. The S strains were pathogenic while the R strains were nonpathogenic. He added the heat-killed virulent bacteria to the live nonvirulent strain and infected mice with it. He showed that the mice developed the disease and were killed. He concluded that a substance from the heat-killed S strains transformed the live R strains into the virulent form that killed mice. However, he could not identify the substance responsible for the process of transformation.