The text plays on the expectation that pressing Control, Alt, Delete is a command on a computer to open the task manager or force a reboot, but humorously suggests it is an 'I.Q. Test', which is not a function of this keyboard command. The joke relies on the incongruity between the expected technical function and the suggested intelligence test, rather than on different meanings of the same word or similar-sounding words.
Press Control , Alt , Delete for an I . Q . Test .