The marketer should go to From Address Management to see a list of all email addresses and domains that are verified for sending1. From Address Management is a feature that allows the marketer to manage, verify, and import email addresses and domains that are used as From addresses in email sends1. The marketer can search, filter, and sort the verified email addresses and domains by status, type, and sendability. The marketer can also add new email addresses or domains, send verification emails, set sendable or non-sendable addresses, and delete unneeded addresses1.
Send Classifications is not the correct answer, as it does not show a list of all email addresses and domains that are verified for sending. Send Classifications is a feature that allows the marketer to define the settings and attributes of an email send, such as the sender profile, delivery profile, CAN-SPAM classification, and priority2. The marketer can use send classifications to choose from a list of verified email addresses or specify a custom email address as the From address, but they cannot see or manage all the verified email addresses and domains in send classifications.
Domain SSL Certificates is also not the correct answer, as it does not show a list of all email addresses and domains that are verified for sending. Domain SSL Certificates is a feature that allows the marketer to enable SSL encryption for their custom domains, which can improve their email security and deliverability. The marketer can use domain SSL certificates to apply SSL encryption to their authenticated or private domains that are used as From addresses, but they cannot see or manage all the verified email addresses and domains in domain SSL certificates. References := 1: From Address and Domain Verification Checklist - Salesforce 2:
Send Classifications - Salesforce : Domain SSL Certificates - Salesforce

A multi-step journey is best suited to run a test between two different versions of an email, such as Einstein Recommendations versus static product recommendations. A single send journey can only send one version of an email to a single audience. A transactional send journey can only send transactional messages that are triggered by API calls or events.

Triggered Automation is a feature that allows marketers to run an automation when a file is dropped into a specified location, such as an FTP folder or Enhanced FTP folder. Triggered Automation can accommodate the setup of NTO's third-party point-of-sale software that sends order information in batches of large files at varying times throughout the day. [Source: Trailhead]

Behavioral Trigger is the correct answer. A behavioral trigger is a type of entry source that allows you to inject contacts into a journey based on their behavior or interaction with your brand. For example, you can use a behavioral trigger to start a journey when a contact makes a purchase on your website, clicks a link in an email, or fills out a form on a landing page. You can learn more about this in the Journey Builder Basics module on Trailhead.

Web Studio to capture Query parameters from social media link is the correct answer. This option allows you to create landing pages or microsites using Marketing Cloud tools and data that can capture information from users who visit your pages from social channels, such as Facebook or Twitter. You can use query parameters in your social media link to pass information such as user ID, name, email address, etc., and then use AMPscript or SSJS code in your Web Studio page to retrieve and store that information in a data extension or list for future mailing. Use Journey Builder to build an audience using Ad Studio is not a valid option, as this option only allows you to create audiences based on existing contacts in Marketing Cloud or Salesforce CRM, not new users from social channels. Use an interactive form from Email Studio to collect this information is not a valid option either, as this option only allows you to collect information from users who already receive your emails, not new users from social channels. You can learn more about this in the [Web Studio Basics] module on Trailhead.