Explanation: 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.