Answer:
I'd say D. Both 'a' and 'b'
Step-by-step explanation:
Outlining your essay prepares you for what you'll write on your paper. When you do you, you figure out your main idea, what direction you'll take your essay, and the evidence you'll use to support your main idea.
I'm not quite sure what the 5 paragraph format is but I'm assuming it's like the 4 paragraph format: Introduction Paragraph, Body 1, Body 2, and Conclusion.
Knowing how many paragraphs you'll be writing can help you plan how you'll spread the information you've gathered throughout your essay.