The Sunspot Cycle on the Sun Is A(n)

The sunspot cycle on the Sun is a(n) :

A) regular movement of a relatively constant number of sunspots from the poles to the equator of the Sun over an 11-year period.
B) somewhat irregular but always present cycle of buildup and decay of sunspot numbers.
C) irregular buildup and decay in the number of sunspots averaging about 11 years, which occasionally fails for a time when no spots appear.
D) extremely regular buildup and decay in the number of sunspots, with a precise period of 11.3 years.