Answer:
Hi! I don't know if there are supposed to be any options because you didn't put any, but I can answer anyways: the purpose of understanding the makeup of your audience is to gain their attention and interest.
Step-by-step explanation:
When creating a speech, or exposition, knowing your audience is a must in order to do a good job. By knowing what kind of people is attending -age, gender, social environment, etc.- you will be able to create a speech in which they will be interested because they will feel that your words represent them. If they don't feel you are talking especially to them and their needs, they will probably lose interest and stop listening to you.