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