How do y’all solve this

Which of the following is not a transverse wave? a) soundb) lightc) radiod) all of thesee) none of these

Two steel balls, each of mass m, are welded to a light rod of length l and negligible mass and are initially at rest on a smooth horizontal surface. a horizontal force of magnitude f is suddenly applied to the rod as shown. determine (a) the instantaneous acceleration a of the mass center g and (b) the corresponding rate at which the angular velocity of the assembly about g is changing with time.

Why does lightning travel from clouds to the ground?