So here are the answers!
1. Left
2. had trekked
3. had visited
4. couldn't
5. bigger
The first three are in psst tense because the events did not happen just now, and could wouldn't make sense for number 4, and number 5, and biggest is not a word.
1: Left
2:Was trekking
3:Has visited
4: Couldn't
5:Bigger
