Whilst the thief was -------------- the passengers kept apologizing for the inconveniences he was causing…

1. Analyze the question The sentence says a thief was doing something to the passengers. The gap needs a verb in the -ing form that matches what a thief does. This is a spelling and vocabulary question, so the main task is to pick the correctly spelled word with the right meaning.

2. Explain the concept Look at how each option is spelled and what it means:

• A. rabbing: not an English word.
• B. rubbing: a real word (to rub, to press against something), but it makes no sense for a thief.
• C. robbing: from the verb rob, meaning to steal from someone by force or threat. The final consonant is doubled before -ing (rob → robbing).
• D. rubbying: not an English word.

3. Solution Whilst the thief was robbing the passengers, they kept apologizing for the inconvenience he was causing them.

The sentence is a bit humorous, since the passengers apologize to the one robbing them. The context still clearly requires "robbing".

4. Answer The correct option is **C.

5. Tip Be careful with confusable pairs like rob/rub. Use meaning to decide:

• Rob = steal (a robber, a robbery)
• Rub = to apply friction (a rubber)

Also remember the doubling rule: a short verb ending in a single vowel plus a consonant doubles that consonant before -ing (rob → robbing, stop → stopping, run → running).