Final answer:
The three primary photo-based social media sites are Fa--cebook, In--stagram, and Tw--itter, which have replaced traditional photo sharing methods such as physical photo albums and earlier digital platforms like Fli--ckr.
Step-by-step explanation:
The three primary photo-based social media sites currently dominating the market are Fa--cebook, Inst--agram, and Tw--itter. These platforms have largely replaced traditional methods of photo sharing such as physical photo albums, sharing printed photos by mail, and earlier digital methods like email attachments or photo sharing websites that preceded the social media boom, such as Fli--ckr or Pic--asa. Social media offers instant communication and the ability to share photos with a broad audience at the click of a button, which contrasts with the slower and more private methods of the past.