Answer:
C). A graph showing the increase in jet speeds over time.
Step-by-step explanation:
Visual aid is described as the graphic or visual illustration of the information presented that assists the readers to understand and memorize the content more effectively. Visual-aid serves to compliment the information through pictorial or visual representation that accentuates the idea or information which helps the audience to affiliate the information and remember it more comprehensively and conveniently. It also functions to authorize the author's reliability by making the content more evident. Thus, option C is the correct answer for the given question as 'the graph'(visual representation) would supplement the information of 'increase in jet speeds over time'.