Which of the following formats uses interlaced scanning?

Interlaced scanning involves displaying the even and odd lines of a frame in alternating sequences, which can enhance the perceived motion quality and reduce flicker in video signals. 1080i is specifically designated as an interlaced format: it means that it has a resolution of 1920x1080 pixels, with the 'i' standing for 'interlaced.'

In contrast, formats such as 720p and 480p are progressive scanning formats. In progressive scanning, all lines of each frame are displayed in sequence, which can result in smoother motion renderings and is often preferred in modern broadcasting. Additionally, 4K refers to a resolution of approximately 3840x2160 pixels and can be either interlaced or progressive, but commonly in practice, it is associated with progressive scanning. Therefore, 1080i is the only format listed that explicitly uses interlaced scanning.