The visual illusion called the Hermann (Hering) grid:

A. can be completely understood based on the receptive field properties of ganglion
B. cells is likely to result from operations at many stages of visual processing
C. is closely related to the scintillating grid illusion
D. has no explanation based on retinal processe

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.