Scientist, a fact is something that can be tested by anyone with the proper skill and equipment, and that repeatedly and reliably gives the same result every time. A scientific theory is a body of knowledge based on facts that describes their interaction in the simplest possible way
They train our immune system so it's ready when our bodies are attacked, and they aid in digestion and supply us with vitamins. ... Scientists and doctors can even utilize prokaryotes to help the human body.
Exceptions to a and b are when volcano forms at hot spots in the middle of Continental plates or oceanic plates.