What Is the Cause of the Sunspot Cycle on the Sun

What is the cause of the sunspot cycle on the Sun?

A) Comets crashing into the Sun cool the photosphere and create sunspots. The 11-year sunspot cycle is the result of an 11-year periodicity in the flux of comets.
B) Subsurface magnetic fields are twisted by the Sun's differential rotation and break through the surface as sunspots, then gradually cancel each other and return below the surface.
C) Differential rotation on the Sun creates eddies, or vortices, that cool the photosphere and create sunspots, then the eddies gradually cancel each other out and the cycle starts over.
D) Subsurface magnetic fields are concentrated by the Sun's differential rotation. These fields remain under the surface and prevent heat from reaching the photosphere, creating sunspots. The concentrated fields gradually cancel each other out, and the cycle starts over.