The pilot or flight attendant __ usually alert during the flight.

Explanation:

the options are "is" and "are"

The pilot or flight attendant is usually alert during the flight.

it's talking about either one noun or the other, not two or more nouns, it cannot be are instead it should be is

they are most likely about to fight in the battle of gaul

voracity is the noun corresponding to the adjective voracious, which means (1) eager to consume a great amount of food, or (2) marked by an insatiable appetite. veracity is far more common than the rare voracity, so the latter is sometimes used in place of the former.