You will match the skier on top of the mountain with the graph on the far left. This is because he has potential energy but isn't moving and therefore has no kinetic energy.
You will match the skier that is half-way down the mountain with the graph in the middle. He is losing potential energy as he starts moving, and gains kinetic energy because he is gaining speed.
You will match the skier at the bottom of the mountain with the graph on the far right. This is because he has reached maximum speed and therefore has the most kinetic energy, and almost no potential energy.
Hope that helps!
