Why Are Sunspots Cooler Than the Rest of the Sun's

Why are sunspots cooler than the rest of the Sun's surface?

A) Sunspots, unlike the rest of the Sun, are made of plasma, and plasmas are difficult to heat.
B) Sunspots mark the pathways along which neutrinos escape from the Sun. Neutrinos move so quickly that they deposit very little energy along their paths.
C) Sunspots occur where the magnetic field lines return into the Sun carrying smaller amounts of heat energy from the thin solar atmosphere.
D) Sunspots mark the places where the magnetic field lines penetrate the Sun's photosphere. The hot solar plasma beneath is repelled from these field lines and thus inhibits the flow of heat to the surface at these points.