The given diagram shows nitrogen cycle in the ecosystem. P, Q, R, S and T represent different chemical conversion steps in the cycle.
Which process (P - T) is correctly paired with the organism's group performing that step?
I. P is Nitrobacter
II. Q is bacteria symbiotic with plants
III. R is denitrifying bacteria
IV. S is nitrifying bacteria
V. T is nitrogen fixing bacteria, such as Rhizobium
or cyanobacteria
AIII, IV and V
BIV and V
CI, III and IV
DIII and IV
Can somebody explain this diagram to me?