What is the critical function of the lateral stabilizer struts or check chains (Seitenstreben / Unterlenker-Stabilisatoren) on a tractor's three-point hitch during road transport?

1. To let the lower links float so the implement can follow ground contours
2. To transfer part of the implement's weight onto the front axle
3. To limit how far the three-point linkage can be raised
4. To lock the lower links rigidly so the mounted implement cannot sway sideways while driving