Question

Coral reefs are one of the most _________, biologically complex, and diverse marine ecosystems on Earth. This ecosystem is one of the ___________ paradoxes of the biosphere : how do clear, and thus nutrient-poor, waters support such ____________ and productive communities ?
 

a) common, sensitive, fruitful

b) fragile, fascinating, prolific

c) deep, strange, exuberant

d) frail, unrecognised, wealthy