Explanation
The HML merge field that should be included in an email to allow prospects to manage their email preferences is {{OptOut}} or {{EmailPreferenceCenter}}. The {{OptOut}} merge field inserts a link that allows prospects to opt out of receiving emails from the sender. The {{EmailPreferenceCenter}} merge field inserts a link that allows prospects to choose which types of emails they want to receive from the sender. The {{Unsubscribe}} merge field is not valid in HML, as it is only used in PML. The {{ReportSpam}} merge field is not recommended, as it can negatively affect the sender's reputation. The {{Opt_Out}} merge field is not valid in HML, as it uses an underscore instead of a camel case1. References: 1: HML Merge Fields

Explanation
The difference between a dynamic list and a static list is that you cannot manually update list membership of a dynamic list but you can manually update list membership of a static list. A list is a collection of prospects that you can use to segment your audience, send emails, or perform other actions. A dynamic list is a list that automatically populates with prospects who match the criteria you set. A static list is a list that you manually populate with prospects or import from a file. A dynamic list is constantly updated, so prospects are added or removed from the list as they meet or no longer meet the criteria. A static list is not updated automatically, so you can add or remove prospects from the list as you wish. You cannot manually update list membership of a dynamic list, because the list is controlled by the criteria. You can manually update list membership of a static list, because the list is controlled by you

Explanation
The following activities would make a prospect active in Marketing Cloud Account Engagement:
* Submitting a Marketing Cloud Account Engagement form, which indicates the prospect's interest and consent to receive communications from the company.
* Clicking on a custom redirect, which tracks the prospect's engagement with external links or
* downloadable content.
* Visiting a Marketing Cloud Account Engagement-tracked page, which captures the prospect's browsing behavior and page views on the company's website. References: [Marketing Cloud Account Engagement Prospect Activities]

Explanation
It is not possible to create a dynamic list of all prospects who have accessed a certain file in Marketing Cloud Account Engagement. Dynamic lists are based on criteria that match prospect fields, not prospect activities.
Therefore, you cannot use a dynamic list to segment prospects based on whether they have downloaded a file, watched a video, or visited a page. Option A is not correct because field value mapping has nothing to do with dynamic lists or file access. Option C is not correct because match type is irrelevant for this question, as there is no valid criterion for file access. Option D is not correct for the same reason as option C.
References: Marketing Cloud Account Engagement Dynamic Lists for Faster Segmentation (+ 10 Examples), Create a Dynamic List - Salesforce

Explanation
According to the Salesforce documentation, the two capabilities that are true for completion actions are: C) Completion actions cannot be applied directly on a landing page, and D) Completion actions do not execute on image file downloads. A completion action is an automation tool that can be used to perform an action after a prospect successfully completes a marketing element, such as clicking a link in an email, submitting a form, or visiting a web page. A completion action can be used to perform actions such as adding a prospect to a list, assigning a prospect to a user, sending an autoresponder email, or adjusting a prospect's score. Completion actions cannot be applied directly on a landing page, as landing pages do not have completion actions.
However, completion actions can be applied on the forms or custom redirects that are embedded on the landing page. Completion actions do not execute on image file downloads, as image file downloads are not considered as completion events. However, completion actions can be executed on other types of file downloads, such as PDFs or Word documents. Completion actions are not applied retroactively, as they are only applied to prospects who complete the marketing element after the completion action is created.
Completion actions do not apply to both visitors and prospects, as they only apply to prospects who have been identified by their email address or their Marketing Cloud Account Engagement tracking cookie.
References: Salesforce documentation