To determine which friend's graph represents a proportional relationship, we need to look for a straight line that passes through the origin (0,0). A proportional relationship means that the number of levels passed should be directly related to the time played, with a constant rate of change.
If you can describe the characteristics of each graph (such as whether they are linear, whether they pass through the origin, or if they have a constant slope), I can help you identify which one shows a proportional relationship.