When a drug is ingested, how does it get into the bloodstream?
a. through the intestines
b. through the stomach
c. through the mouth
d. all of the above?

b. through the stomach

Explanation:

A drug is a substance which is capable of bringing the physical and physiological change in an organism when taken either orally, intravenously, subcutaneously, smoked or inhaled.

The drug which is taken orally or ingested enters the elementary canal. It is dissolved inside by the fluids in stomach, then absorbed by the bloodstream through the linings of the stomach and later by the intestine.      

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.