To determine the order of the runners from most improved to least improved, we need to consider their times compared to their personal bests. A negative number indicates an improvement, and a positive number indicates a slower time compared to their personal best.
Here are the times:
- Gregor: +5.6 (5.6 seconds slower than his personal best)
- Hiroki: -11.6 (11.6 seconds faster than his personal best)
- Isabelle: +3.2 (3.2 seconds slower than her personal best)
- Juan: 0 (equal to his personal best)
- Karen: -5.2 (5.2 seconds faster than her personal best)
To rank them from most improved to least improved:
1. Hiroki: -11.6 (most improved, since his time is the fastest compared to his personal best)
2. Karen: -5.2 (second most improved, also faster but not as much as Hiroki)
3. Juan: 0 (no improvement, but no decline either)
4. Isabelle: +3.2 (slower than personal best, less decline than Gregor)
5. Gregor: +5.6 (least improved, slowest compared to his personal best)
Thus, the correct order from most improved to least improved is:
Hiroki, Karen, Juan, Isabelle, Gregor
Hence, the correct list is:
```
Hiroki, Karen, Juan, Isabelle, Gregor
```
