Based on the information provided, the line that indicates the distance run in relation to time for each participant is as follows:
- Bella: 3.5 km in 45 minutes
- Ruby: 2.5 km in 40 minutes
- Greg: 2.5 km in 45 minutes
- Paul: 1 km in 25 minutes
From the details given, Greg is the person who ran 2.5 km in 45 minutes. Therefore, the correct response is:
Greg