Based on the reading by Maryboy and Begay (2010), which best describes the cycle of sunspot activity?
1) The cycle of sunspot activity is irregular and unpredictable.
2) The cycle of sunspot activity follows a predictable pattern with a period of approximately 11 years.
3) The cycle of sunspot activity is influenced by human activities.
4) The cycle of sunspot activity is directly related to the Earth's magnetic field.