Based on the information provided, the person who ran 2.12 km in 45 minutes is Greg. This is inferred because Greg's line passes through the point (45, 2.5), indicating a distance of 2.5 km in 45 minutes.
However, since the question asks for 2.12 km, it’s likely there may be a detail not explicitly stated in the problem. The closest match based on the provided data would still lead to Greg.
Thus, the answer is Greg.