The Broadcast View of Q&A is designed to be shared with the audience on a big shared screen. It includes the URL for attendees so everyone can see where they should submit their questions.
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You can find the broadcast view for Q&A in the upper right corner, under the Settings gear. Hover over Broadcast to show Slideshow and Feed views.

The Q&A Feed View shows a list of the submitted questions in upvoted order.

The slideshow view shows only one question at a time. You can switch between questions in several ways. 

When you're in the Presenter view, you can click on a question to set it to broadcasting. Click on "Broadcast" to switch to that question automatically.
Note: this will also change the Feed View to show only that question.

You can also switch the question displayed while you're in the Broadcast View. You can swipe left or right. Plus you can click-drag or use the arrow keys on your keyboard.
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In slideshow mode, the broadcast view will cycle through the approved questions, pausing for a few seconds on each.

In the lower right corner, you'll see an Enable Slideshow option. 

This option is disabled by default, but you can enable the slideshow by clicking the link in the lower-right corner.