This question is testing PARALLELISM and MEANING.

When we see "... , and prompts..." we know that we're looking for a parallel list: X, Y, and Z. Just note: we don't have to make every verb in the sentence parallel! You might be looking for:
... the surge has clogged air traffic control... , lead to delays..., and prompted fears...
That would be structurally parallel. But... these aren't 3 separate actions. The 2nd two are the result of the 1st one.

The more clear meaning would be to make the first verb the main verb, and have the other 2 modifying:
... the surge has clogged air traffic control... , leading to delays..., and prompting fears...

(A) to lead to 55 percent more delays at airports, and prompts
- "to lead... and prompts" is not parallel
- "to lead" implies intention - that this happened in *order* to lead to these delays, etc.

(B) leading to 55 percent more delay at airports and prompting
- "leading and prompting" is parallel, but...
- "more delay" is not idiomatic

(C) to lead to a 55 percent increase in delay at airports and prompt
- same issue with "to lead" as in A
- "increase in delay" not idiomatic

(D) to lead to an increase of 55 percent in delays at airports, and prompted
- same issue with "to lead" as in A

(E) leading to a 55 percent increase in delays at airports and prompting
- "leading and prompting" is parallel
- "increase in delays" is correct

The answer is E.