Whilst the thief was _____ the passengers kept apologizing for the inconveniences he was causing them.
Answer Details
The word that best fills the gap is "robbing."
"Robbing" is a verb that means to take something by force or threat of violence. In this sentence, the thief is taking something from the passengers and they are apologizing for the inconvenience he is causing them.
Therefore, the correct sentence is:
"Whilst the thief was robbing, the passengers kept apologizing for the inconveniences he was causing them."