What must a Slider ad display before user interaction?

The correct choice is that a Slider ad must display an overlay slider before user interaction. This requirement is rooted in user experience standards and best practices in interactive advertising. An overlay slider offers an engaging way for users to interact with ads without disrupting the overall browsing experience.

An overlay slider typically presents additional content, calls to action, or visual elements that can be manipulated by the user, enhancing interactivity. By requiring this initial display, advertisers ensure that users are aware of the interactive nature of the ad and are encouraged to engage with it actively.

The other options do not align with the interactive functionalities necessary for Slider ads. A full-screen format may be too intrusive, fixed dimensions do not necessarily communicate interactivity, and placeholder text lacks the visual appeal and engagement factor of an overlay slider. Thus, the requirement for an overlay slider is essential for both user understanding and effective ad performance within the digital landscape.