Reference the following code snippets that allow a form to function correctly.

The correct code to insert at the EXPRESSION placeholder in the ISML template snippet to ensure the form functions correctly is pdict.newsletter (Option B). This variable likely contains the form data being passed to the template via the controller, which aligns with typical naming conventions and practices in SFRA where the pdict (Page Dictionary) object holds all data relevant to the current page context. This ensures that form inputs and actions are properly linked to their corresponding data handled in the server-side script.