How were dead S-type cells able to transform living
R-type cells?

Griffith concluded that in the presence of the dead S-type pneumococcus cells, some of the living R-type cells had been transformed into virulent S cells. These cells were able to grow in the bodies of the mice, causing pneumonia and multiplying in the blood. ... The DNA alone caused bacterial transformation.

Griffith introduced heat-killed 'S'- strain bacteria Streptococcus in to a mouse along with live 'R' strain bacteria. ... Some 'transforming principle' transferred from the heat-killed 'S' strain had enabled the 'R' strain to synthesise a smooth polysaccharide coat and become virulent.

In this experiments, Griffith injected mice in the lab with live R-type of bacteria. They did not suffer from the disease. ... He thus concluded that heat-killed smooth type bacterial caused a transformation of the living rough type bacteria. This experiment suggested that DNA and not proteins are the genetic material.

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.

the correct answer is d