How Does the Number of Sunspots on the Sun Vary

Multiple Choice

How does the number of sunspots on the Sun vary with time?

A) The number of sunspots varies relatively regularly, with a period of about 11 years.
B) The number of sunspots varies irregularly, with no periodicity.
C) The number of sunspots increases and decreases with a precise period of 11.1 years.
D) The number of sunspots increases for about 11 years and then decreases again over the next 11 years.