Well let's start off with all the people:
Chantelle is running with sandals ( which is not very wise because you can trip eaisly in sandals)
Sarah is running with the lowest stride possible, so that means she is running the shortest length at her race pace, or even faster than her race pace. But since it is the shortest stride, it is most likely her normal race pace.
Kevin is running with his hands at his chest. Which is a good way to run, however it may depend it he has his hands are closed into a fist, or if they are open were you can see is hands.
Chris is running the longet stride which means he is going the most distance, which also means he is running faster than his race pace which is not good for you.
So my answer would be kevin is running in the best form.
If you need more help with this subject then feel free to pm me :)
Have a nice evening