The correct option is C. In order to gather details about your topic you should determine audience and purpose.
Knowing your purpose and audience helps determine your strategy.
When you communicate, your purpose is not what you want to do; instead, it is what you want your audience to do afterf reading what you wrote or listening to what you said. Thus, it engages the audience. To communicate effectively, you must adapt to your audience. Therefore, you must know your audience.