The author's attitude to the ecological situation of the tropical forests is ______.

A．more buildings erected in the forests
B．fig trees planted in all forests
C．scientific efforts diverted to bomb making
D．the preservation of as many diverse species as possible

A．research into tropical-forest biology on Barro Colorado Island
B．how the whole ecosystems can depend on the survival of a single species
C．the life cycle of the fig wasp
D．the importance of forests to the human race