Explanation
Marketing Cloud Account Engagement forms are the best option if you need to be able to edit and change your form directly. Marketing Cloud Account Engagement forms are built and managed completely in Marketing Cloud Account Engagement, and you can easily modify them using the form builder or the layout template.
You can also preview and test your changes before publishing them. Form handlers, on the other hand, require you to edit and change your form on the external platform where it is hosted, and you may need to regenerate the code snippet if you add or remove any fields

According to the Salesforce documentation, the actions that can be done with the gear icon on the prospect list are: B) Assign, C) Delete, and D) Edit. The gear icon is a feature that allows users to perform different actions on a prospect or a group of prospects from the Prospect List. The gear icon can be accessed from the Prospects tab in Marketing Cloud Account Engagement, and it can show different options for the selected prospect or prospects, such as assign, delete, or edit. The assign option allows the user to assign the prospect or prospects to a user, a group, or a queue. The delete option allows the user to delete the prospect or prospects from Marketing Cloud Account Engagement. The edit option allows the user to edit the prospect or prospects' information, such as name, email, or custom fields. The copy option is not an action that can be done with the gear icon on the prospect list, as it is not an available option for the prospect or prospects. Reference: Salesforce documentation

Explanation
According to the Salesforce documentation, the types of fields that are not supported by the Marketing Cloud Account Engagement sync are: B) Formula fields, D) Geolocation fields, and E) Text Area (rich) fields. A Marketing Cloud Account Engagement sync is a feature that allows users to connect and exchange data between Marketing Cloud Account Engagement and Salesforce fields, such as name, email, score, or grade. A Marketing Cloud Account Engagement sync can be configured by the administrator in the connector settings, and it can be customized for different objects, fields, or actions. A Marketing Cloud Account Engagement sync can support different types of fields, such as text, number, date, checkbox, picklist, or lookup fields.
However, a Marketing Cloud Account Engagement sync cannot support some types of fields, such as formula, geolocation, or text area (rich) fields. A formula field is a field that calculates a value based on a formula or an expression. A geolocation field is a field that stores the latitude and longitude coordinates of a location. A text area (rich) field is a field that allows users to enter formatted text, images, or links. These types of fields are not supported by the Marketing Cloud Account Engagement sync, as they are either incompatible, complex, or large for the data exchange. A record type field is a type of field that is supported by the Marketing Cloud Account Engagement sync, as it is a field that defines different business processes, page layouts, or picklist values for different users. A number field is also a type of field that is supported by the Marketing Cloud Account Engagement sync, as it is a field that stores numerical values. References: Salesforce documentation

Explanation
Visitors are anonymous web browsers who have interacted with your online marketing content, such as your website, landing pages, or custom redirects. Visitors are converted to prospects when they fill out a form or form handler, which captures their email address and other information. Filling out a form or form handler is the only way to convert a visitor to a prospect. Running through completion actions, matching an automation rule, or visiting a Marketing Cloud Account Engagement landing page do not convert visitors to prospects, unless they also fill out a form or form handler on those pages. References: Visitors and Prospects, Forms and Form Handlers

Sales users are Marketing Cloud Account Engagement users who have access to the prospect database and can send one-to-one emails to prospects, but not list emails. Sales users can also view and edit prospect records, create tasks and activities, and sync prospects with Salesforce. You can set up sales users in Marketing Cloud Account Engagement by assigning them the Sales role and enabling the one-to-one email option in their user settings. Reference: [User Roles], [Create and Edit Users]