To enable a data extension for MobileConnect single SMS sends, Marketing Cloud requires two specific, correctly-typed fields rather than generic text or number fields. First, the mobile number must be stored in a field explicitly configured with the Phone field type (B), which Marketing Cloud recognizes and validates specifically for SMS-sendable data extensions — a generic Number field type (A) does not carry this recognition and would not enable the data extension for SMS sending. Second, a Locale field (C) is required to inform MobileConnect of the appropriate regional/country context for correctly interpreting and formatting the phone number for delivery, since SMS delivery requires country-specific routing and formatting logic that the Locale field supplies. Option D, a generic Text field manually formatted to contain the country code plus mobile number, does not satisfy Marketing Cloud ' s structural requirement for a properly-typed Phone field — the platform specifically looks for the Phone field type to recognize a data extension as sendable for SMS, regardless of whether the text content itself happens to be correctly formatted. Consultants should treat the combination of a dedicated Phone-type field and a Locale-type field as the mandatory structural prerequisite for any SMS-sendable data extension. Reference: MobileConnect Sendable Data Extensions, Field Type Requirements.