Why Is the Temperature at the Region of a Sunspot

Why is the temperature at the region of a sunspot cooler than the photosphere?

A) Sunspots are holes in the photosphere that reveal the lower-temperature gases in the deeper layers.
B) Sunspots represent points where streams of cool gas from the corona lower the temperature in those regions of the photosphere.
C) Powerful magnetic fields in the sunspots act upon the atoms of the photosphere to prevent them from emitting light.
D) Powerful magnetic fields in the sunspots inhibit the convective flow of the gases of the photosphere downward, allowing the area to cool for longer than would normally be possible.