What is the meaning of “Built In” in TV Ads ?

• A. An advertising with a form of writing that appears on the screen to explain about a product.
• B. An advertisement that fills a portion of a segment in a TV program and usually equipped with some demo or tutorial to using the product.
• C. The advertising that usually used as a property stage.
• D. An advertisement that delivered by the host in the middle of program or event.