Based on the context, what is the best definition of the word illusion?

Voice is the varying of pitch when speaking.

Alert inattentive or drowsy drivers when they veer off the road ?

For the speaker, which of the following is a less distracting and easier approach than using a presentation outline? a. using post-it notes, color coded b. using notecards c. using full sheets of lined notebook paper d. using the preparation outline