A:
According to HP:
Some HP printers use five HP 564, 364, 178 or 862 Ink Cartridges: Black, Cyan, Magenta, Yellow, and Photo.
Other HP printers use only four 564, 364, 178 or 862 Ink Cartridges: Black, Cyan, Magenta, and Yellow.
It is easy to tell whether or not a printer requires a Photo cartridge:
If it has slots for four cartridges, it does not use a Photo cartridge
If it has slots for five cartridges, it does use a Photo cartridge
It is also easy to tell the difference between Black and Photo cartridges at the store: Photo cartridges have a picture of a camera on them, and are named Photo Ink.
Do not buy Photo cartridges for printers that do not use them.
NOTE: Black and Photo cartridges are not interchangeable. Photo cartridges cannot be substituted for Black cartridges.
Do not expect Photo cartridge test patterns on diagnostic pages to be pure black - the ink is actually gray.