In the context of the input sentence, determine the relationship between 'comScore' and 'Rentrak'.
Options: platform, location of formation, owner of, founded by

Despite serving as a punching bag for media executives frustrated by mobile video, Nielsen is unlikely to be knocked from its perch as the industry standard for buying and selling advertising even as leading rivals  Rentrak ( RENT - Get Report ) and comScore ( SCOR - Get Report )  plan to merge.
owner of