Long-Exposure Color Photographs of the Night Sky Often Show Regions

Long-exposure color photographs of the night sky often show regions that glow red, such as the Rosette Nebula in Figure 13-8 in the text. This distinctive red color is caused by the

A) emission of red and infrared light by warm dust grains.
B) collective glow of many red giant stars in the region.
C) scattering of starlight by dust grains in the nebula.
D) ionization and subsequent recombination of hydrogen atoms.