If industrial pollution continues to deplete the ozone layer, the resulting increase in ultraviolet radiation will endanger human helth, causing a rise the incidence of skin cancer and eye disease, and perhaps even threatening global ecological syste.

A. and perhaps even threatening

B. and may even threaten

C. and even a possible threat to

D. as well as possibly threatening

E. as well as a possible threat to

需要解释， answer is Ｂ, 最迷惑于 Ａ，Ｂ中

这个题目考察的其实是对并列结构的判断, 即到底哪个threaten是和cause并列 还是和endanger human health并列

很容易看出 威胁全球生态系统 应该是和危害人生健康并列的 所以应该选择B

希望这个简单的解释可以帮到你