Refer to the input text as context and select the correct relationship between 'Apple Inc' and 'iPhone' from the available options.
Options: currency, owner of, product/material produced, platform

Barron's said investors in GoPro are "skittish" about the company's ability to ward off competition from Apple Inc (APPL.O), which has upgraded the camera on its iPhone to produce more high resolution video.
product/material produced