Final answer:
The Maunder Minimum and the Little Maunder Minimum were periods with the lowest sunspot numbers, while the sunspot maximum occurs approximately every 11 years, with the last one occurring in 2014.
Step-by-step explanation:
The years that had the lowest number of sunspots were during a period known as the Maunder Minimum, which occurred from 1645 to 1715. During this time, even at sunspot maximum, the sunspot numbers were significantly lower than average. Another period of low sunspot activity, termed the Little Maunder Minimum, occurred during the early years of the nineteenth century.
In contrast, periods of high sunspot activity, or sunspot maxima, occur approximately every 11 years, with the number of sunspots varying each cycle. The last sunspot maximum occurred in 2014, where more than 100 sunspots could often be seen at once, though this still represented less than one-half of one percent of the Sun's surface covered by spots.