Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to add files to a memory stick [title] Locate your pc's usb port. [step] Usb ports are rectangular with a solid piece of plastic on the upper half of the slot and an empty space on the bottom. The port should have a graphic of three branching arrows pointing upward (or downward, depending on your pc) next to it.

Ending1: [substeps] If you have a full-sized usb drive, a hard drive mounted by a computer could fit inside. Make sure it's plugged in before attempting to take more than one drive. Ending2: [substeps] If you're using a desktop, your usb ports are most likely integrated into the cpu, while laptop usb ports are usually on the left or right edges of the casing. [title] Plug your memory stick into the usb port. Ending3: [substeps] If your pc has to connect both personal and work computers, note that this method does not allow for the installation of an optical drive. [title] Insert your optical drive into the cd drive. Ending4: You'll need the usb port to run a window that lets you view, edit and upload files on the same drive or with the same system. [substeps] The usb port is located on the lower left corner of the drive to the right of the cd/dvd drive.

Answer format: ending1/ending2/ending3/ending4