Which of the following is the best description of protists' contribution to photosynthesis?
-about 30% of the worlds photosynthesis is performed by protists
-Protists carry out the majority of the worlds photosynthesis
-only terrestrial protists subbstantially contribute to photosynthesis
-the net effect of protists is to impede photosynthesis by parasitizing plants
-protists play an important role only through symbioses with photosynthetic organisms