the phrase

the resulting increase in ultraviolet radiation

have 2 consequences
1. endanger human health, causing a rise in the incidence of skin cancer and eye disease

2. perhaps even threatening global ecological systems

obviously, the tense of the 2nd one follows the 1st one.

Clarity is being tested in this question.

Let's analyze the idiom--if industrial pollution...then(is actually omitted), the resulting increase in .....will endanger....

Now let's analyze your E. as well as a possible threat to. It's wordy

Compare E to B. Choice B is clear and concise.

Remember, when answering for SC, start with the choice that has the least amount of words. If it's clear and concise, then select that one. Also, one final point, if you analyze choice B, it modifies the subject industrial pollution. I choice E, you can't clearly distinguish what's being modified, whether it's industrial pollution, the ozone layer or something else.

I hope this helps.

Andrew

a real test of parallelism...


will endanger human health...... and may even threaten

i hope u got it???

thanks for the clarification. i always thought "threat to" was an idiom.