asasasas1

will endanger human health and perhaps even threaten global eco. systems

causing .... 是同位语修饰 human health 的。

如果选 A 的话， endanger ..., causing ..., and threatening ..., 不能平行的。

如果你认为后面两个causing..., and threatening ... 并列的话，那么其间的逗号应该省略的呀。