Select the verb form that most appropriately completes the following sentence:-

My sister ____ me once or twice since the time she moved to Athens.

has messaged

The correct answer is Option (2):has messaged*

This sentence requires the Present Perfect tense (has messaged) because:

1. Action from Past to Present: The action of messaging started in the past (when she moved to Athens) and continues to be relevant up to the present moment.

2. Completed Action with a Count: The phrase "once or twice" indicates a completed number of actions. The Present Perfect (has messaged) is used to describe actions completed at an unspecified time before now, or actions that have occurred a specific number of times in a period leading up to the present. 

   Why Other Options Are Incorrect:

• was messaging (Past Continuous): Used for an action ongoing in the past.

• has been messaging (Present Perfect Continuous): Used to emphasize the duration or frequency of an action, usually implying a continuous activity (e.g., "She has been messaging me all day"). It conflicts with the limited count of "once or twice."

• had been messaging (Past Perfect Continuous): Used to describe an action ongoing before another past action. (e.g., "She had been messaging me for an hour before she called."