Final answer:
To display a blank black slide during a presentation, press the 'B' key. Press it again to return to the previous slide, which helps focus the audience's attention away from the slides momentarily.
Step-by-step explanation:
During a presentation, you can display a blank black slide by pressing the B key. When you are ready to resume your presentation, simply press the B key again to return to the slide you were displaying.
This technique can be particularly useful when you want to focus the audience's attention on what you're saying or to take a break without having the slide content displayed in the background.