An experiment you have been conducting uses a large pond to observe how the input from fertilizer runoff affects the native pond community.You find that many amphibians are not able to survive in this pond when the nitrogen levels are high.What could you do next to best test if nitrogen concentrations affect amphibians?

A) Do a field experiment to exclude amphibians from the pond and see if they survive elsewhere
B) Experimentally raise frogs in a controlled laboratory experiment where some are exposed to water from the pond at certain periods of time and others only raised in filtered water for the duration of the experiment.
C) Find other ponds and input runoff to see if amphibians there cannot survive too
D) Increase the runoff input at your pond and see if amphibian survivorship decreases