A marketer is completing a checklist prior to deploying an email, what action will
validate feature completed when initiated

A healthcare company imports its patient portal registrations at the parent level business unit (BU). The marketing team would like to ensure individual office locations have access to this data without giving access to the parent level BU.
What should the marketing team do in Automation Studio to ensure data is available at the child BU level?

Northern Trail Outfitters wants to ensure that the Email Address field value is not duplicated in a data extension. What should a marketer do to ensure the Email Address field values are unique?

A marketer at Northern Trail Outfitters must design a targeted email campaign for the company's new winter offerings. What email best practice should be used?

Northern Trail Outfitters (NTO) receives a complaint from a long-time customer who claims that, despite providing an updated email address, they are still receiving emails at an old address. NTO confirms that the customer's new email address is stored in the target data extension.
What is preventing the customer from receiving emails at their new address?