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.
Take context from the input text and decide on the accurate relationship between 'Viacom' and 'CBS' from the options provided.
Options: subsidiary, member of, stock exchange, chairperson