GRE Text Completion: Fundamental 24 Sets-GRE填空基础24套 - W10NGRYEB0L0Z5BB!

Because howler monkeys rarely come out of the trees in their arboreal habitat, the continued well-being of the rain forest is ____________ to their survival. A. marginal B. tangential C. indispensable D. imperative E. expeditious F. baneful