A researcher is recording and monitoring data about a population of plankton-eating fish. When she analyzes the data, she notes a population change that starts at point D.



Which is the best prediction to test in an investigation to explain why the population changed at point D?

a
The number of predators in the area has decreased.
b
Increased water clarity caused an increase in plankton density.
c
People released an invasive species of fish into the ecosystem.
d
The fish entered into a mutualistic relationship with another organism.

b

Increased water clarity caused an increase in plankton density.