If it is ‘height from the ground’, it would be a ‘positive’ graph because you would be above the ground the whole time.

If it is ‘personal height’, it would be ‘no correlation’ because riding a ferris wheel does not increase or decrease personal height.

My guess is that the teacher will accept either answer with supporting evidence.

Now, you’re up the top of the wheel and the height is, say, 10m and time now is, say, 120s.

Finally, you’re coming down to the ground again and your height is 0m and time now is, say, 240s.

If you plot those three points on to a Cartesian Plane, you will be able to see/deduce that your Height-versus-Time graph will (or should) look like a parabola with a maximum. This is provided that the wheel gives you a smooth ride.