What tense is represented by the statement "They had already left by the time I arrived."?

The statement "They had already left by the time I arrived." is in the Past Perfect tense. This tense is used to indicate that one action was completed before another action took place in the past. In this case, 'had left' signifies that the action of leaving occurred before the action of arriving.

The use of "had" plus the past participle "left" clearly indicates the Past Perfect tense. It helps establish a timeline, showing that the departure was completed prior to the speaker's arrival. This clarity about the sequence of events is essential in understanding relationships between past actions. The Past Perfect tense is commonly used to illustrate such relationships in narrative contexts, emphasizing how one event impacts another.

In contrast, the other options do not accurately reflect this structure or function. The Present Perfect tense indicates actions that connect to the present, Future Perfect Continuous focuses on actions that will be ongoing up to a specific point in the future, and the Past Simple refers simply to actions that occurred in the past without the nuance of one event preceding another.