I would put time on the x axis, and height on the y axis - the height is the thing you're measuring so it's the dependent variable, which always goes on the y axis :)
Errors are that the graph does not start and end with zero. Since it's a rollercoaster it was at rest before they rode it, and so the time must start from 0 seconds, not 2 seconds. It must also come to a stop at 0 seconds, not 2 seconds.