What is the function of the commutator in a dc motor? to spin the magnet to change direct current into alternating current to change alternating current into direct current to spin the wire coil

Commutator is an attachment, connected to the armature of motor or generator through which electrical connection is made and ensures that the current is flowing like a direct current
And it is a device for reversing the direction of flow of electrical current.
In addition by using induction the current is induced in a circuit due to a change or motion in a magnetic field is so directed as to oppose the change in flux "is the surface magnetic divided by time" and to exert a mechanical force opposing the motion of the spin of wire coil. 

Iread this book last year so take this with a grain of salt.gene jumps from the tree to compete with finny due to the fact that gene is always trying to do better than finny. he is put under the grasp of peer pressure due to finny almost forcing him to do this. ever since he first jumped finny kept pressuring him to jump since he thought gene enjoyed jumping.rather than uses this answer you should probably just reread chapters 3-4