The marketing manager of Northern Trail Outfitters is interested in A/B testing emails in order to increase subscriber engagement.
Which two practices should the marketing manager employ? (Choose two.)

Northern Trail Outfitters (NTO) plans to launch an email campaign. They have two data extensions. The Mountain Manor Campaign data extension will contain the sending audience for this campaign and includes fields for Email Address, Full Name, Loyalty Member ID, and Loyalty Member Status. NTO will be using AMPscript to reference data in a second, nonsendable data extension named Loyalty Member.
Which field on the Mountain Manor Campaign data extension should be created as a Primary Key to create unique relationships with the Loyalty Member Profile data extension?

Identify the bestpractices for interacting with potential and active subscribers. (Choose 3)

A marketer wants to grow the company's email subscriber list via social channels and its mobile app. Which best practice can the marketer use to grow the subscriber list? (Choose 2)

Northern Trail Outfitters wants to send shipping email notifications to members, Shipping fulfillment data is included in a file that is moved at frequent intervals to a folder on their Enhanced SFTP Account.
Which solution could be used to achieve this?