A is the answer. They use this to reason with one person.
The correct answer is A. You can receive instant feedback from your audience.
This is something that cannot be done if you are writing a text and your audience reads it at their home - they cannot immediately let you know what they think about your ideas and arguments. However, if you are giving a speech in front of an audience, then they absolutely can. B, C, and D are examples of what happens during writing, rather than speaking.