Explanation: In a raster scan display, the entire image data is stored in a digital memory area, often called a frame buffer. Each pixel or group of pixels on the screen corresponds to a specific address or range of addresses within this memory. If a portion of this memory fails, the data for that corresponding screen region will be corrupted or unreadable. When the display attempts to retrieve and display this faulty data, it will result in a blank or corrupted *rectangular block* on the screen, directly reflecting the memory area that has failed. Horizontal sweep circuit issues would typically affect entire scan lines or horizontal synchronization across the screen, not a confined rectangular block. A general power supply problem would likely cause the entire display to fail, be dim, or exhibit widespread issues, not localized to a specific rectangle. Similarly, a fault in the vertical blanking pulse would affect the overall frame synchronization or vertical retrace, causing full-screen rolling or retrace lines, not a rectangular hole in the video.