In his work with pneumonia-causing bacteria and mice, Griffith found that

a. the protein coat from pathogenic cells was able to transform nonpathogenic cells.

b. heat-killed pathogenic cells caused pneumonia.

c. some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.

d. the polysaccharide coat of bacteria caused pneumonia.

Option (c).

Explanation:

Griffith is known as the father of transforming principle. He worked on the virulent and a virulent bacteria that causes pneumonia. He done his experiment on different heat conditions.

When he heat killed the S strains of bacteria and R strains of bacteria into the mice, the mice was killed. He concluded that there was some substance or transforming principle converts the non pathogenic bacteria into the pathogenic strain.

Thus, the correct answer is option (c).