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

Embryonic stem cells are cells derived from an embryo. these cells can be used to create new tissues for patients suffering from certain illnesses and disorders. which statement best summarizes why the use of embryonic stem cells could be seen as unethical? a. some people consider embryos to possess rights equal to those of fully developed human beings. b. extracting stem cells from embryos is a very energy-intensive process, which consumes resources that could be used elsewhere. c. embryos are difficult to obtain, so the monetary cost of using them for research outweighs their benefit. d. the process of extracting stem cells from embryos generates biohazardous waste that cannot be safely disposed of.