Viacom (NasdaqGS: VIAB - news ) fell 7.5 percent, 21st Century Fox lost 7.0 percent, CBS shed 4.6 percent and Comcast dropped 4.7 percent.
Analyze the relationship between 'Viacom' and 'CBS' within the context of the input sentence.
Options: chairperson, founded by, employer, parent organization