One Reason to Know Your Presentation Well Before You Face

One reason to know your presentation well before you face the audience is so that you can

A) ask questions to gauge the audience's knowledge of the topic before you begin speaking.
B) practice adjusting the microphone's audio feedback and volume at the start of your talk.
C) use jargon and slang if appropriate for all listeners.
D) maintain eye contact with members in all corners of the room as you speak.
E) speak more quickly than normal and make all your points before time runs out.