Multiple choice: Sunspots appear dark because
(a) they are patches of the photosphere that occasionally burn up, creating soot;
(b) the changing magnetic polarity of the Sun causes gas in the sunspot to cool down substantially;
(c) they are regions in which strong magnetic fields make it difficult for fresh supplies of hot, ionized gas to reach the photosphere;
(d) they are much hotter than the surrounding area, so their emission peaks at ultraviolet wavelengths, which our eyes cannot see; or
(e) they are holes in the photosphere through which the cooler interior of the Sun is visible.

Sunspots appear dark because they are regions in which strong magnetic fields make it difficult for fresh supplies of hot, ionized gas to reach the photosphere.

Sunspots are typically cooler than their surroundings. For example, the temperature of a large sunspot can be about 4,000 Kelvin which is lower than the temperature of the photosphere around it which is about 5,800 Kelvin.