If you have more than 50,000 subscribers your test distribution should be what percent per condition?

Which feature would a marketer use to build a Send Classification? (Choose 2)

Northern Trail Outfitters (NTO) has a small catalog of items featured in company emails. The NTO marketing team manages what images, copy, suggested items, and call-to-action are used with each item in this catalog within a database. This data is saved into a data extension in Marketing Cloud and then called into the emails dynamically.
Each time a change is made to the content, a new, updated file is dropped on NTO's SFTP. A proof email is
then sent to business stakeholders for final approval.
Using Automation Studio, how can NTO ensure that the catalog stays up-to-date?

Northern Trail Outfitters wants to ensure its emails are meeting subscriber expectation
and enticing engagement.
Which 2 best practices should NTO employ when sending email?

Northern Trail Outfitters (NTO) sends a hiking newsletter to an audience that has opted to receive messages about hiking. They have noticed in the last six months their open and click rates have been trending lower. NTO wants to reverse this trend.
How should they improve their engagement rates with unengaged subscribers''