You should do every option in an extemporaneous speech except a. commit your speech to memory.
Memory is very important when giving a speech, but it is not the most reliable tool you have in your presentation. Nerves and stage fright could be some of your most powerful enemies when you are on the spotlight, and they will always attack your memory first.
So, writing some notes, making a keyword outline and rehearsing carefully are the best options to give your best speech!
