Moderators have the option of requiring their approval of a question that is submitted before it is visible to the audience. We call this the 'Q&A Approval Filter'. 

When the Q&A Approval Filter is enabled, the questions that your audience submit will not appear on the page until a moderator approves them.

The Q&A Approval Filter is disabled by default. To enable it, go to 'Session Settings' and choose 'Enable/Disable Features, and then click the lock icon next to the Q&A Filter text.

Questions waiting for approval will be visible on the Moderator page, and you'll see an "approve" button on the left hand side -- a plus-sign icon.

To approve a question, simply click on the plus-sign icon on the left-hand side.

Once a question has been approved, it will appear on everyone's page and attendees can then up-vote it.