You can send an automated email to a prospect after they fill out a form using either an automation rule or a completion action. An automation rule is a criteria-based action that is triggered when a prospect matches the rule. You can use an automation rule to send an email to prospects who fill out a specific form or any form. A completion action is a task that is performed after a prospect successfully completes a marketing element. You can use a completion action to send an email to prospects who fill out a particular form. You cannot use a segmentation rule to send an email, since segmentation rules are used to segment prospects into lists or update their field values. Reference: [Automation Rules], Completion Actions, [Segmentation Rules]

A prospect is automatically removed from future email sends when they either hard bounce or soft bounce five times. A hard bounce occurs when an email is permanently rejected by the recipient's server, usually because the email address is invalid, non-existent, or blocked. A soft bounce occurs when an email is temporarily rejected by the recipient's server, usually because the mailbox is full, the server is down, or the message is too large. A hard bounce indicates that the email address is no longer valid and should be removed from your list. A soft bounce indicates that the email address may still be valid, but there is a temporary issue that prevents the delivery. However, after five soft bounces, Marketing Cloud Account Engagement will mark the prospect as undeliverable and stop sending emails to them

The email in Step 3: Send email "Getting Started" will be received by the prospect on Monday, if the prospect starts the drip program on Wednesday. A drip program is a program that allows you to send a series of emails to your prospects based on a predefined schedule and logic. You can use drip programs to nurture your prospects, educate them about your products or services, or encourage them to take action. You can also use drip programs to send emails only during business hours, which are the hours that you specify for sending emails to your prospects, such as 10am - 4pm M-F. To calculate when the email in Step 3 will be received by the prospect, you need to follow the drip logic and the business hours settings. The drip logic is outlined below:
Start
Step 1: Send email "Welcome."
Step 2: Pause 3 days.
Step 3: Send email "Getting Started."
Step 4: Pause 7 days.
Step 5: Send email "Tech Setup."
Step 6: Pause 7 days.
Step 7: Send email "Complete Configuration."
End
The business hours settings are:
Only send emails during business hours (10am - 4pm M-F)
Assuming that the prospect starts the drip program on Wednesday at 10am, the email in Step 3 will be received by the prospect on Monday at 10am, following this logic:
Wednesday 10am: The prospect starts the drip program and receives the email in Step 1.
Thursday 10am: The prospect is still in Step 2, which pauses for 3 days.
Friday 10am: The prospect is still in Step 2, which pauses for 3 days.
Saturday 10am: The prospect is still in Step 2, which pauses for 3 days. However, since it is not a business day, the pause does not count.
Sunday 10am: The prospect is still in Step 2, which pauses for 3 days. However, since it is not a business day, the pause does not count.
Monday 10am: The prospect completes Step 2, which pauses for 3 days, and moves to Step 3, which sends the email "Getting Started." Therefore, the email in Step 3 will be received by the prospect on Monday at 10am.

Explanation
According to the Salesforce documentation, an automation rule is an automation tool that can be used to send an email to a prospect when a form is submitted and a specific field value is selected on that form. An automation rule can be configured to trigger an action (such as sending an email) when a prospect meets certain criteria (such as submitting a form and having a specific field value). The criteria can be set to Match All or Match Any, depending on the logic required. In this case, the Match All option should be used, as the prospect needs to meet both conditions (form submission and field value) to receive the email. A completion action is another automation tool that can be used to perform an action after a prospect successfully completes a form, but it cannot be used to check for a specific field value. A dynamic list is a list of prospects that is updated automatically based on certain criteria, but it cannot be used to send an email directly. A list email is an email that is sent to a specific list of prospects, but it cannot be triggered by a form submission or a field value. References: Salesforce documentation

Explanation
Email, First Name, and Last Name are not required fields in order for GoToWebinar to register a new user to an event. GoToWebinar is a web conferencing platform that allows you to host and join online meetings, webinars, and trainings. You can integrate Marketing Cloud Account Engagement with GoToWebinar using the GoToWebinar connector, which allows you to register prospects for GoToWebinar events from Marketing Cloud Account Engagement forms, landing pages, or completion actions. However, the only required field for GoToWebinar registration is Email. You can also include other fields, such as First Name, Last Name, Phone, or Company, but they are not mandatory. If you do not include these fields, Marketing Cloud Account Engagement will use the default values from the prospect's record or the connector settings.
Answer A is incorrect because Email, First Name, and Last Name are not required fields in order for GoToWebinar to register a new user to an event, as explained above. References: [GoToWebinar Connector],
[Set Up the GoToWebinar Connector]