Not C here. File sharing link (B) is the only way reps can give files to customers without needing to set up external access like Experience Cloud. Chatter link looks tempting, but it won’t work if the person isn’t already inside Salesforce. Agree?
Easy to miss that C might work if the customer is already created as a community/external user, but the question says no Experience Cloud site. That rules it out, so B fits best for non-Salesforce users. Pretty sure that's how Salesforce does file access in this sort of case-correct me if I'm missing a scenario?
Think I'd say C here just because Chatter lets you post links to files and mention people, so reps could tag the customer if they're already in the org. Only works if the external user has some level of access though, which might be a gap. Anyone else run into this restriction?