PATHOGENS

[Russ]

Go with the first one, less likely to be marked wrong I guess

[Panku_0117]

as a matter of fact, there are many kinds of species in the world, both parasite and virus could be the pathogens. pathogens are the organism which can cause other one ill or medical record.

[slothpomba]

Pathogens really are more indicative of an agent that "spreads" something, in this case a disease.

Cancer causes ill to the organism but cant spread (for all intents and purposes here). Most cancers are caused by mutations in the cell (for those of you who know the exceptions i didnt mention it because it could confuse the VCE people) and so you really cant get cancer from a pathogen.

So a pathogen is more something that spreads disease rather than what you stated above.

Infact if you break it down into the greek used to make the word (very useful tool in biology i think):
Patho - Means "Disease"
Gen - To produce something/cause something/make something come about