What screen size is required for full screen graphics in HD video?

The correct answer is based on the definition of HD video. Full HD, which is considered the standard for high-definition video resolution, is 1920 by 1080 pixels. This resolution ensures that the video is displayed in the highest quality available for standard HD content, providing a clear, sharp image that fully utilizes the screen's capabilities.

In contrast, the other resolutions listed do not meet the specifications for full HD. The resolutions of 640 by 280 and 1280 by 720 are considered lower definitions, with 640 by 280 being quite far from high-definition standards and 1280 by 720 being classified as HD, but not full HD. The 3840 by 2160 resolution is classified as 4K, which is a higher standard than full HD, but it doesn't apply to the question of what is required specifically for full screen graphics in the context of HD video. Thus, 1920 by 1080 is the benchmark resolution for achieving full screen graphics in HD video.