To determine who ran 2.12 km in 45 minutes based on the graph's data, we look for the participant whose line corresponds to this distance at that time.
From the description:
- Bella ran 3.5 km in 45 minutes.
- Ruby ran 2.5 km in 40 minutes.
- Greg ran 2.5 km in 45 minutes.
- Paul ran 1 km in 25 minutes.
None of the mentioned participants ran exactly 2.12 km in 45 minutes. However, Greg is the one who ran for 45 minutes and covered a distance closest to the specified distance (2.5 km).
Thus, the best response based on the options provided is:
**Greg**