The concept of 'Ecological Transition' was first used by

1. A

   Elton

   Charles Elton is associated with the niche, food chains and animal ecology, not the phrase ‘ecological transition’ in this item.

2. B

   Bennett

   John W. Bennett used ‘ecological transition’ (The Ecological Transition, 1976) for the shift in how human societies use and transform ecosystems. That is the official key.

3. C

   Berkeley

   Berkeley here is a distractor (school/place name), not the anthropologist of this concept.

4. D

   Ratzel

   Friedrich Ratzel is anthropogeography and Lebensraum, not Bennett’s ecological transition.

Summary. Official key is (b) Bennett. Keep Elton for classical ecology, Ratzel for political geography, and Bennett for cultural-ecological transition. Honour the stored letter (b).