Explanation
When an engagement studio action step is scheduled to send an email on a specific date, it means that the email will be sent to all prospects who reach that step on or after that date. Therefore, a prospect arriving after the send date will be sent the email (D). The prospect will not remain on the step until a new send date is set (A), skip the Send Email step (B), or be removed from the program. References: Work with Time and Pauses in Engagement Studio

Explanation
A prospect is a visitor who has submitted an email address through a form or landing page on your site. This is the primary way that Marketing Cloud Account Engagement identifies and converts visitors into prospects. A prospect can also be created from an email link click, a manually entered email address, or an import.

A landing page without a form is the Marketing Cloud Account Engagement asset that an administrator would create to advertise an upcoming event's schedule without requesting information from those who visit. A landing page is a web page that can display any content, such as text, images, videos, or links. A form is a web element that can collect information from visitors, such as name, email, or preferences. A landing page with a form, a landing page with a form handler, or an email template with a form embedded into the HTML are not suitable for advertising an event's schedule without requesting information, as they all involve forms that require visitor input3. Reference: 3: [Landing Pages and Forms]

Explanation
Marketing Cloud Account Engagement forms are the best option if you want to use progressive profiling to personalize your form. Progressive profiling is a feature that allows you to display different fields on your form based on what you already know about the prospect. This way, you can avoid asking the same questions repeatedly, and instead collect more relevant and valuable information over time. Form handlers do not support progressive profiling, and will always show the same fields on your form

You can preview or test matches for automation rules before you run them by using the automation preview option. This option allows you to see how many prospects will be matched by your automation rules without actually running them. You can access this option by clicking the Preview button while the rules are in Paused mode. You will receive an email notification when the preview is finished or you can wait on the page for it to finish in real-time. The preview will tell you how many prospects will be matched and show you a sample of them. If you adjust criteria on existing automation rules, please note that automation previews will identify only prospects who have not already had the rule's actions applied to them.
Answer A is incorrect because running the automation rule will not only show you how many matches there are, but also apply the actions to them, which may not be what you want. Answer C is incorrect because creating a list and seeing how many prospects are affected will not give you the same results as the automation preview option, since the list criteria may not match the automation rule criteria exactly. Answer D is incorrect because there is no such option as the prospect table actions. References: Automation Rules, Preview Automation Rules