Astronomers have concluded that the Sun's activity varies in an 11-year cycle. Which of the following statements about this cycle is TRUE?
a. The Sun's activity cycle shows absolutely no connection to its magnetic field.
b. When sunspots are at a minimum we get the largest number of flares and prominences.
c. The number of sunspots gets larger and smaller over the course of 11 years.
d. Every 11 years sunspots completely cover the Sun making its surface much darker.