Terrance is going on the road to show how the world’s climate has been changing. He is going to show how the polar ice caps have receded over time. He will be speaking in auditoriums around the country, and in each case the audience will likely have at least 150 people. His presentation was created in Prezi and contains no more than seven lines of text, each with no more than seven words. He was sure to plan for a medium that would keep his listeners’ attention while never straying from the relevance of his presentation. What rule for using visual aids was Terrance considering above all?