Complete the sentence using the correct options:-

When I reached the station, the train

had already left

The correct answer is Option (3) - had already left

The correct answer is had already left. ✅

Explanation:
The action of the train leaving happened before the action of you reaching the station.
So, we use the past perfect tense → had already left.

Complete sentence:
When I reached the station, the train had already left.