A certain lake in the arid west contains an endangered species of fish. The legal status of this ...

A certain lake in the arid west contains an endangered species of fish. The legal status of this fish required water diversions out of the river feeding the lake to be decreased substantially.
 
  About 10 years following this decree, the declining cottonwood forest and canopy along the riverbanks was noted to be recovering. This situation illustrates the potential effectiveness of
  a. the species approach to sustaining biodiversity
  b. the ecosystem approach to sustaining biodiversity
  c. cottonwood trees as part of all stream recovery programs
  d. water as a solution to species decline
  e. fish as indicator species