Explanation
The Einstein STO activity allows the journey to send five different versions of an initial welcome email to new subscribers at the optimal time for each subscriber. This activity requires only one email and one activity, whereas the Join activity would require five emails and five activities.

Explanation
After a Contact Delete request has been processed for subscribers who have been sent an email previously, the following data would still exist in the account:
* Contact-specific data at the job level. This includes data such as open rate, click rate, bounce rate, and unsubscribe rate for each individual contact who received an email. This data is not deleted because it is used for reporting and analytics purposes.
* General tracking data at the job level. This includes data such as total number of sends, opens, clicks, bounces, and unsubscribes for each email job. This data is not deleted because it is used for reporting and analytics purposes. The other options are incorrect because:
* Contact data in non-sendable data extensions. This includes data such as name, address, phone number, and other attributes for each contact. This data is deleted because it is not used for sending emails and it is considered personal information.
* Contact data in sendable data extensions. This includes data such as email address and subscriber key for each contact. This data is deleted because it is used for sending emails and it is considered personal
* information.

Explanation
To resolve the issue of not being able to see the audience file in the data extension when scheduling the send, the admin should confirm that the data extension is marked as Sendable. A sendable data extension is one that has an email address field and a subscriber key field that can be used for sending emails. If the data extension is not marked as sendable, it will not appear as an option when selecting an audience for an email send. The other options are incorrect because:
* The data extension contains a Salesforce ID. This is not a requirement for sending emails from a data extension. A Salesforce ID is only needed if NTO wants to use Marketing Cloud Connect to sync data between Marketing Cloud and Salesforce CRM.
* The Data extension is marked as Sendable and Testable. This is not a valid option for marking a data extension. A data extension can only be marked as sendable or non-sendable; there is no testable option.
* The data extension is linked using the Contact Key. This is not a requirement for sending emails from a data extension. The Contact Key is only needed if NTO wants to use Contact Builder to link data across different sources and channels.

Explanation
To create and schedule a weekly report with high-level metrics, the Marketing Cloud admin should use Analytics Builder. Analytics Builder allows users to create, view, and share reports and dashboards. The Account Send Summary report shows how many emails were sent in a given time period