text: C.  Symbiosis involves a relationship by which both partners give something to the relationship.  A pathogen only takes, but does not provide.  \n\nFor A,  the human intestine provides food, and the bacteria produce vitamins.  For B, the bacteria aid in pollination and once again are provided with a food source.  For D, bacteria once again have a food source (and even outcompete) and thus help provide protection.   And E, the bacteria fix nitrogen for the plants' survival and get a place to live and food.\n\n\nThe key to convergent evolution is that the two species are not closely related, eliminating B and D.  The process involves the independent acquiring of similar traits due to similar environmental pressures.  This points us to E.