What is the relationship between Viacom and CBS in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

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.

Answer: parent_organization