Which statements describe ways in which heat can be generated?

by rubbing two sticks together, enough heat can be generated to start a camp fire.
1) heat energy is generated by ice when it is melting.
2) heat can be created when tires roll on paved highway roads on a long road trip.
3) gravity generates heat by pulling solar energy toward earth's surface.
4) water creates heat energy when it condenses to form clouds.
5) burning broken tree limbs and other yard scraps creates heat energy.