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.