Pick out all the instances of discourse reference in the following text. At one point the

Brundtland report states that " The loss of plant and animal species can greatly limit the options of future generations; so sustainable development requires the conservation of plant and animal species". What, all of them？ At what price？ ... At another point the Brundtland report says that economic growth and development obviously involve changes in the physical ecosystem. " Every ecosystem everywhere cannot be preserved intact. " Well, thats a relief. But how can it be made consistent with the earlier objective？ Does it mean that it is all right to deprive some people in some parts of the world of a piece of their ecosystem but not others？ What justification is there for this discrimination？