Comprehensive and Detailed Explanation:
Correct answers are A, C, and D.
* A - Long and Short Codes are country-specific; availability must be checked per country.
* C - Inbound messaging (users texting keywords to subscribe) generally requires local Short or Long Codes.
* D - MobileConnect is not supported in every country; Salesforce provides a list of supported regions.
#Why others are wrong:
* B: Customers are billed by Salesforce, not directly by the mobile carriers.
* E: Opt-ins can occur via Web Forms, Mobile Keyword responses, or API - not only via inbound messaging.
Exact Extract from Salesforce Official Documentation:
Salesforce Help - MobileConnect Considerations:
"Short and long code availability is country-specific. Inbound messaging requires a local code.
MobileConnect is not available in all countries."
(Source:https://help.salesforce.com/s/articleView?id=sf.mc_ms_considerations.htm)
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