#Comprehensive and Detailed Explanation: The correct approach isone Parent Business Unit (corporate) with one Child Business Unit per franchise owner. This setup allows:
* Corporate to control global assets, subscriber management, and brand compliance.
* Franchise owners to localize messages within their own Business Unit, without accessing or changing corporate-controlled assets.
#Why Other Options Are Incorrect:
* A: "Franchise owners" (plural) need individualized control; a single child BU won't be sufficient.
* C: One Business Unit won't provide separation between different franchise operations.
* D: Having a separate parent BU for each franchise is excessive, costly, and not scalable.
Exact Extract: Salesforce Help:Business Unit Overview
"Use Business Units to manage assets, permissions, and subscribers separately while maintaining corporate brand control across an enterprise."

* To prevent duplicate Contact records, the customer needs to update the current All Subscribers list and Contact model by migrating the Subscriber Key to match the Sales Cloud ContactID or LeadID (B).
* Uploading a CSV with the new Subscriber Keys mapped appropriately will ensure that existing records are updated (A).
Simply continuing as normal (C) will not prevent duplicates because Email Address is not unique enough across Salesforce objects. Full purge (D) is unnecessary and risks data loss.
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Exact Extracts from Salesforce Documentation:
Source: Salesforce Help - Subscriber Key and Contact Key Best Practices
# "When integrating Sales Cloud, update existing Marketing Cloud subscribers to match the Salesforce ContactID or LeadID as Subscriber Key to prevent duplicate contacts." Source: Salesforce Implementation Guide - Marketing Cloud Connect Setup
# "Migrating existing contacts requires careful key management to align records across systems without duplication."
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Using "Define Subscriber Filter" at the BU level allows you to limit subscribers based on Profile Attributes like "Region." Each child BU will then automatically filter the All Subscribers list and other sendable data based on that Region, ensuring users in a BU can only access subscribers for their specific region.
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Exact Extracts from Salesforce Documentation:
Source: Salesforce Help - Define Subscriber Filters for Business Units
# "Subscriber filters allow you to limit the subscribers available to users in a business unit based on Profile Attributes. Define a condition such as Region = 'West' to restrict subscribers to a particular group."
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When a new user registers through the mobile app, and the ContactKey isn't immediately set, the MobilePush SDK assigns a temporary identifier (a GUID) to the device.This results in the creation of a new Contact in Marketing Cloud.Once the user's information is synced from Sales Cloud and the ContactKey is established, the device can be correctly associated.However, until this association occurs, the system treats the device as belonging to a separate, anonymous contact.
Reference:
Salesforce Developers:Register Contacts with Marketing Cloud Engagement

To resolve the issue of new contacts not receiving SMS messages due to missing country codes in the mobile number field, the best solution is to select 'Normalize Phone Number' in Journey settings .
* Normalize Phone Number : In Journey Builder's SMS activity settings, enabling the "Normalize Phone Number" option automatically formats phone numbers to the E.164 standard (e.g., +1 for US numbers) by appending the appropriate country code based on a specified default country (in this case, the United States). This ensures that phone numbers missing a country code are correctly formatted for SMS delivery.
* Why it works :
* SMS providers require phone numbers in E.164 format (e.g., +12025550123 for a US number).
* If the mobile number in the Salesforce Entry Data Extension lacks the country code (e.g.,
2025550123), the SMS will fail to send.
* Normalizing phone numbers at the journey level corrects this issue without requiring manual updates to Salesforce records.
Why the other options are incorrect:
* A. Select 'US' as the sending country in SMS activity : The sending country setting in MobileConnect determines the short code or long code used for sending, not the formatting of recipient phone numbers. It does not address missing country codes in the data.
* B. Format the phone field in Salesforce as +1[phonenumber] : While manually formatting phone numbers in Salesforce to include the +1 country code would work, it requires updating all existing records and implementing validation rules for new records, which is inefficient and prone to errors compared to normalization.
* D. Configure the phone field in Salesforce as US locale : Setting the phone field's locale in Salesforce affects display formatting (e.g., (202) 555-0123) but does not automatically add the +1 country code in the E.164 format required for SMS.
Exact Extract from Salesforce Documentation:
* Normalize Phone Number : "When you enable Normalize Phone Number in an SMS activity, Marketing Cloud automatically formats phone numbers to include the country code based on the selected country, ensuring compliance with E.164 standards for SMS delivery." (Source: Salesforce Help - MobileConnect SMS Activity Configuration )
* E.164 Format : "SMS messages require phone numbers in E.164 format, which includes the country code (e.g., +1 for the United States). Use normalization to correct improperly formatted numbers." (Source: Salesforce Help - MobileConnect Best Practices )