When do cells differentiate? That is, when do cells first become different kinds of cell-muscle cells, nerve cells, reproductive cells,
etc?

they deliver oxygen to the blood

i think it’s c but i might be wrong. if i am let me know! have a good rest of your day as well!

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.