Each 720p video frame contains how many horizontal lines?

The correct choice indicates that each 720p video frame contains 720 horizontal lines. The "720" in 720p refers specifically to the vertical resolution of the video, meaning that there are 720 scan lines or horizontal lines in each frame. This resolution specifies that the video is displayed progressively, which is indicated by the letter "p" in 720p, suggesting that all lines are refreshed in one pass, leading to smoother motion and better visual quality compared to interlaced formats.

The other options represent different resolutions that do not apply to 720p. For instance, 480 refers to standard definition (SD) video formats, 1080 corresponds to high definition (HD) formats like 1080p, and 1440 is associated with higher resolutions such as 1440p, which is not relevant to 720p specifications. Understanding these resolutions helps in distinguishing the qualities and capabilities of various video formats.