Answer: B. Gestures
Step-by-step explanation:
[A] You, usually, always want to have eye contact or be facing your audience, so A is not our answer
[B] B is a good answer. You can gesture to the audience to bring attention to a visual aid without disrupting your speech.
[C] Pronunciation may not draw the audience's attention to a visual aid, so option C probably isn't our answer.
[D] You don't want to yell at your audience or lower your voice, so volume, option D, probably isn't our answer.