Answer:
It would be Option B, everywhere.
Step-by-step explanation:
With the sentence that goes along with the word, it fits nicely, suggesting that the smoke is everywhere. Since the smoke was everywhere they couldn't see.
The dictionary definition for ubiquitous is:
ubiquitous
{yoo-bik-wi-tuh s] adjective
existing or being everywhere, especially at the same time; omnipresent: