factory farming is a major contributing to water and air pollution as well as deforestation
The stomach is an organ located predominately in the Left Upper Quadrant (LUQ). The main responsibility of the stomach is to dissolve the ground up food approaching from the mouth through the esophagus, and break it down so it would be to a point wear nutrient could be absorbed.
To donthis task, the stomach must employ, as mentioned Salts and Enzymes, but the most important bit is a very strong acid; Hydrochloric Acid. Your stomach is one of the few organic things that can withstand such an acid.
The answer is A because you track everything.
Pretty sure it is pathogens including bacteria, viruses and protozoans. its not the first and last for sure