When potassium is in high supply, two species of algae have higher growth rates in the presence of each other than they do alone. When potassium is in short supply, species A still performs better in the presence of species B, but species B is not affected by the presence of species A. The increase in potassium thus changes a relationship of _______ to one of _______.

a) 

amensalism; commensalism

b) 

commensalism; mutualism

c) 

commensalism; consumer-resource

d) 

commensalism; amensalism

e) 

amensalism; mutualism