Correct graph for induced E.M.F
The mathematical relation behind the EMF is described by F = q(v x B).

The velocity of the bar normal to the B field is $$V = V_{\text{max}}
   \sin(\omega\ t)$$

It's therefore clear that (4) is also wrong. This follows also by our experience because (4) would mean that a net positive force is acting on the Ferris wheel in the direction from M to L. That would also produce heavy forces in electromotors in axial direction.

To decide between the two remaining possibilities you need to apply the right-hand rule. The thumb of your right-hand points into the direction of v, the indicator into the direction of B. Your middle finger shows you where the force is pointing. As the force in question points from M to L, (3) must be the correct graph.