Final answer:
The impact of public speaking on individuals' performance varies, as evidenced by the differing quality of Shannon and Tracy's class presentations when compared to their practice sessions. Personal levels of anxiety and individual responses to audience presence are key factors that influence this impact.
Step-by-step explanation:
Based on the student presentations described, we can conclude that option D) The impact of public speaking on performance varies between individuals is the most likely scenario. Shannon's improved performance suggests that she thrives in a public setting, perhaps due to an audience's presence enhancing her focus or energy. On the other hand, Tracy's decreased performance in a public setting suggests she may experience higher levels of public speaking anxiety, resulting in a less effective presentation than when she practiced alone. This variability is well-documented: some speakers, like students in a class presentation, may become energized by an audience, while others may become more nervous and inhibited.
The provided information indicates that public speaking's effect on an individual's performance can be quite complex and is influenced by various factors, including personal levels of anxiety, preparation methods, and the individual's response to an audience. It is important for both Shannon and Tracy to understand their own responses to public speaking and to strategize ways to improve their performance, such as practice, relaxation techniques, or seeking feedback.