why past participle

[sanjib]

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
OA is BWhy not A or C

[rahulg83]

https://www.beatthegmat.com/if-industria ... 28433.html

[mbadrew]

This question tests your knowledge of parallelism. Endanger, rise and threatening doesn't sound to good. How about Endanger, Rise and Threaten.

A--uses threatening

B--uses threat. Threat is fear perceived by a person. However, threaten is to project fear. So, there's the difference.

[sanjib]

thnks again for the clarification