<em>babbling</em>: you will start using empty words and will repeat them or you will make incomprehensible sounds. This will show you have not prepared any clear ideas in your speech.
<em>running out of time</em>: If you have not timed your speech, you will probably have more arguments than time. Therefore, you will not have the necessary time to give your speech, which will be too long for the alloted time.
<em>finishing too quickly </em>: This will be similar to the explanation above but in this case your speech will be too short for the alloted time.
I would say 'all of the above' since you could be mumbling (babbling), going at a very slow pace (running out of time) , and speaking too fast (finishing too quickly). Hope that helps :D
