The correct answer is C. Speak a bit more loudly, tell a funny story, and move around a bit more
Explanation:
In some cases during speeches and presentations, the speaker might find the audience is not engaged into the process of listening as expected this has multiple causes including lack of interest of the audience in regards to the topic presented, little interaction between the speaker and the audience, lack of understanding and even external and internal distractions. In these cases, the speaker would need to modify the speech to directly address this problem and make the audience be engaged with the speech.
In general terms directly asking the audience to pay attention and stop being distracted or repeating the information is not effective, instead the speaker should catch the attention of the audience by increasing the amount of positive interaction with the audience and trying to make the speech more conversational and friendly, this includes changes in the voice, especially speaking a bit loudly, asking question to the audience, moving around the space and even telling jokes or anecdotes to catch their attention. Considering this, in the case presented in the question in which the audience are teenagers and are distracted the best option to engage them is to "peak a bit more loudly, tell a funny story, and move around a bit more".