The condition when Kelly offers free 15 minute massage to the participants of a popular 5K race event is an example of co-branding.
A type of marketing strategy in which two or more brands are being promoted in a single event or a campaign with a joint agreement, is known as a marketing method of co-branding.
Hence, option A states about co-branding.
Learn more about co-branding here:
https://brainly.com/question/12436812
#SPJ1