Certain bacteria living in a human's large intestine to produce vitamin k. the intestines are a safe place for the bacteria to live, with plenty of food available. this relationship is an example of a) animal parasitism. b) plant parasitism. c) commensalism. d) mutualism.

A. mutualism
Both organisms benefit from this relationship, which is why it is called mutualism. The human gets vitamin K and the bacteria get a place to live. Commensalism is when one organism benefits and the other is not affected. Parasitism is when one organism benefits at the other organisms expense.

That is true! many fish species traveled to the u.s. because of it.