A pressing issue rare species be on the edge of extinction A pressing issue is that many rare species are on the edge of extinction.

雅思经典必背表语从句一个迫切的问题是许多稀有物种正处于灭绝的边缘？

Breeding centres such as Chengdu are needed to stop giant pandas teetering on the edge of extinction.

成都大熊猫基地的任务就是为了挽救这种濒临灭绝边缘的动物。