Explanation
A random split activity is an automation studio activity that randomly splits a data extension into multiple groups based on percentage or number of records. It can be used to create test groups for different messaging strategies or to segment a large audience into smaller batches for sending. It can handle up to 12 groups and up to 50 million records per group. References:
https://help.salesforce.com/articleView?id=sf.mc_as_random_split_activity.htm&type=5

Explanation
A consideration that should be made when building dynamic content rules is that rules should be built before uploading the respective content. Dynamic content rules are rules that define what content should be displayed based on subscriber attributes or behaviors. Dynamic content rules should be created before uploading content blocks or images into Content Builder, as they cannot be edited after content is uploaded. References:
https://help.salesforce.com/s/articleView?id=sf.mc_ceb_dynamic_content_rules.htm&type=5

Explanation
Supporting inbound messages in each country would require additional long code implementation for MobileConnect. A long code is a standard phone number that can send and receive SMS messages. Each country has its own regulations and requirements for long codes, so a single long code cannot be used for all markets. The other functionalities do not tie to additional long code implementation. References:
https://help.salesforce.com/s/articleView?id=sf.mc_moc_long_codes.htm&type=5

Explanation
How to determine engagement should be resolved prior to generating the audience for sending a special discount offer to engaged customers on their email list. Engagement is a measure of how subscribers interact with emails, such as opening, clicking, or converting. Different criteria can be used to define engagement, such as frequency, recency, duration, or channel preference. Determining engagement can help segment the audience and target the most relevant customers for the offer. References:
https://help.salesforce.com/s/articleView?id=sf.mc_es_engagement_split.htm&type=5
https://help.salesforce.com/s/articleView?id=sf.mc_es_engagement_metrics.htm&type=5

Explanation
Two solutions that could pull in the RSS feed at the time of send for Northern Trail Outfitters' weekly email newsletter are:
AMPscript. AMPscript is a scripting language that can be used to retrieve and display dynamic content from external sources, such as RSS feeds, in emails.
External Content. External Content is a feature that allows marketers to create blocks of content from external sources, such as RSS feeds, in Content Builder.
Dynamic Content is not a solution for pulling in RSS feeds, as it is used to display different content based on subscriber attributes or rules. Personalization Strings are not a solution for pulling in RSS feeds, as they are used to display subscriber or account information in emails. References:
https://developer.salesforce.com/docs/atlas.en-us.noversion.mc-programmatic-content.meta/mc-programmatic-co
https://help.salesforce.com/s/articleView?id=sf.mc_ceb_external_content_blocks.htm&type=5