Review the images on the left.

First drop-down: flex boxes

Second drop-down: background-size

Third drop-down: cover

The correct layout mechanism is responsive flex boxes because the content changes from a vertical mobile arrangement to a wider multi-column layout as space becomes available. Flexbox supports this behavior naturally through flexible item sizing and wrapping, often without needing explicit media queries for every screen size. The header image must fill its visible header region on both mobile and desktop. The correct CSS property for controlling how a background image scales inside its container is background-size. The correct value is cover, because background-size: cover scales the image so that the entire container is covered while preserving the image’s aspect ratio. This prevents distortion, although some cropping can occur when the image and container have different aspect ratios. contain would preserve the full image but may leave empty space. auto would use the image’s intrinsic size and would not reliably fill the header area. background-attachment, background-clip, and background-repeat do not control image scaling.