Successful parasite

[Navin]

thanks a lot everyone. Now i understand the answer.

[kokigami]

I am gonna bump this up to kinda steal the thread.

I am new here, and on another forum I was in an arguement which revolved around the definition of parasite. More specifically, if a fetus met the definition. I content it does. But I am not a biologist. Nor, I think, were any of those who were arguing against the idea.

In terms of the original question, I would agree that only B works.

A would be a symbiot
C would not be required, and would actually reduce the available food supply for itself and its species
D would also be irrelavant.

As I can tell, a parasite is defined only in its relationship to its host. That relationship being parasitic...

A parasite need not even be a living thing. An air conditioner unit is parasitic to an automobile engine (where as an alternator is symbiotic).

Since answering the original question is dependent upon how one defines what a parasite is.. I feel my tangent is worth discussing.

Thanks.