What action should a marketer take to add a subscriber to a data extension and send a thank-you email using Smart Capture?

To successfully add a subscriber to a data extension and send a thank-you email using Smart Capture, the appropriate action is to add to the Data Extension. Smart Capture is a feature used in Marketing Cloud that enables marketers to create forms for collecting subscriber information directly. When a visitor fills out the Smart Capture form, the captured data can be automatically saved into a specified data extension.

By choosing to add the subscriber to the data extension, the marketer ensures that the person's information is stored appropriately for future communications and campaigns. Following the addition of the subscriber, the marketer can then leverage automation features to trigger a thank-you email, solidifying the relationship with the new subscriber immediately.

The other options, while related to data management and email sending, do not directly fulfill the requirement of adding a subscriber into a data extension through Smart Capture. Refreshing the data filter does not add new subscribers but rather updates the existing data view; sending an email via Triggered Send involves a different process that requires prior subscriber existence in the system; and simply adding a new subscriber to a list does not integrate with the Smart Capture functionality, which focuses on data extensions for more dynamic subscriber management.