Marketo provides a specific embed code type called "Lightbox" to display a form within a pop-up modal window on an external website. When a marketer approves a form, they can access the "Embed Code" action. Within the embed code options, selecting "Lightbox" generates the necessary JavaScript to render the form in an overlay on the host page. This is the standard and most direct method to achieve the desired outcome without requiring additional modules or complex workarounds.

B. Design a landing page that gives the visual effect of a pop up window

This is an inefficient workaround, not a direct feature. It involves creating a separate page rather than integrating a pop-up directly onto the existing company website.

C. Change the form type to Lightbox under form settings

This option does not exist within the form editor's "Form Settings." The display behavior (e.g., lightbox, embedded) is determined by the embed code generated, not a setting on the form asset itself.

D. Create a New RTP Dialog Web Campaign

While a Real-Time Personalization (RTP) Dialog campaign can display a form in a pop-up, this is a feature of a separate, more advanced Web Personalization module. The most fundamental method uses the form's own embed code functionality.

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1. Adobe Experience League - Marketo Engage Documentation: Embed a Form on Your Website.

Section: "Embed Code"

Content: This document explicitly details the steps to get a form's embed code. It lists the "Code Type" options, which include "Lightbox." The description for Lightbox confirms it makes the form "appear in a lightbox when a user clicks a link on your page." This directly supports option A as the correct method.

2. Adobe Experience League - Marketo Engage Documentation: Form Settings.

Section: "Settings" under "Form Editor"

Content: This documentation outlines all available settings within the form editor, such as Font Family, Font Size, and Label Position. It confirms there is no setting to change a "form type" to Lightbox, which invalidates option C.

3. Adobe Experience League - Marketo Engage Documentation: Create a Dialog Web Campaign.

Section: "Web Campaigns"

Content: This document describes the process of creating a Dialog (pop-up) campaign using the Web Personalization feature (formerly RTP). It shows that this is a distinct process from embedding a standard form, involving campaign creation, segment definition, and content selection, thus making option D a different, more complex solution than what is required by the question.