For a mobile-first external identity use case, Salesforce requires both the right base license and the right verification channel entitlement. External Identity licenses support authentication for external users such as consumers, while SMS verification credits support sending one-time verification codes to mobile phones for passwordless or verification-based login experiences. Email verification credits would address email delivery, not SMS-based verification. Identity Connect is unrelated because it is an AD synchronization product for workforce identity, not a CIAM licensing option. The architecture requirement here is straightforward: external users authenticate to Salesforce-backed digital experiences, and mobile number verification is part of the sign-in model. That combination points to External Identity plus SMS verification capacity. This is why options A, D work together as the correct solution.