If the tubes of the tracheal system in insects were longer, this would a. allow oxygen to reach the cells faster b. slow down the rate of diffusion c. leave room for a ventilation system d. cause oxygen to reach the cells more slowly

i think that is new experiments yield untrustworthy data and should be carefully considered, because you don't know what will happen with the experiments.

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.