The correct option is D both b and c
Griffith with his experiments on a bacterium, Streptococcus pneumoniae first identified the presence of some genetic material. He did not, however, infer the biochemical nature of the genetic material.
Avery, MacLeod, McCarty first established that DNA was the genetic material by working on the same bacteria as Griffith. However, they could not convince all the biologists.
The unequivocal proof that DNA is the genetic material came from the experiments performed by Alfred Hershey and Martha Chase. They worked with bacteriophages (virus that infects bacteria).