Aclean environment is critical to human health around the world. which statement best summarizes the air pollution situation in mexico city? a) all cars in mexico run on ethanol, not gasoline. b) mexico city has some of the cleanest air in the world. c) students are learning about the negative effects of air pollution. d) only government officials can own cars.,

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.