Salesforce explicitly lists an important limitation for the Marketing Cloud Next Prospect object: a prospect can't directly be added to a Salesforce Campaign as a Campaign Member. Campaign Member relationships use supported CRM person records, principally Leads and Contacts. Therefore, if the business process requires an actual Campaign Member record, the prospect must first be converted or otherwise represented as a supported Lead or Contact.
This doesn't mean prospects are unusable for marketing. Marketing Cloud Next can ingest and manage prospects, create related Individual records in Data 360, include them in Unified Individual processing, score them, segment them, and nurture them. Salesforce also supports converting qualified prospects into Leads or Contacts when they reach the appropriate stage.
Option B is incorrect because using an Audience Flow doesn't remove the underlying Campaign Member object limitation. Option C is also incorrect; activating the campaign doesn't change the supported record types for Campaign Members.
The uploaded master bank keys A. Salesforce's current Prospect considerations explicitly state that a Prospect can't be added to a campaign as a campaign member.
Study Guide Reference: Data Modeling, Identity Resolution and Segmentation → People Records → Prospects, Leads, Contacts, and Campaign Members.
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