Question

Griffith's experiments along with Avery, MacLeod and McCarty helped to determine the transforming factors of Pneumococcus bacteria. Using heat-killed S-strain bacteria and one particular fraction of the cell lysates, they were able to demonstrate that _____ and not ______ was responsible for the basis of lethality of the strain.

a. proteins, DNA
b. DNA, proteins
c. deoxyribonuclease, mucous coat
d. polysaccharides, proteins

Believe the answer is "b" but can't reason it. can someone help me? thanks