Which of the following is a common type of expansion slot?

AGP, or Accelerated Graphics Port, is a common type of expansion slot that was specifically designed for graphics cards in computer systems. This slot provided a point-to-point connection to the CPU, allowing for increased bandwidth and improved graphics performance compared to previous standards. The introduction of AGP allowed for more direct communication between the graphics card and the motherboard, thereby enhancing the speed at which data could be processed and displayed.

In contrast, USB, HDMI, and Ethernet do not fall under the category of expansion slots. USB (Universal Serial Bus) is used primarily for connecting peripheral devices. HDMI (High-Definition Multimedia Interface) is used for transmitting audio and video data to displays, while Ethernet is a standard for networking and connecting to the internet. None of these serve the purpose of expanding the system through dedicated internal slots like AGP does.