请教：白勇题目详解2－45

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

答案：B

这是一个简单的平行对称的题，请教未划线部分的causing似乎不对称啊？

causing ...部分是修饰endanger human health的，

endanger 和  threaten 平行。