Answer:
1. Topic.
2. Main idea.
3. All three? I don't understand what you were trying to say in the question. If you meant what to do to look for the main idea of a text, all of the above should be correct.
Explanation:
It is B! Purpose means why
I think It's A
intro
explains what about
Answer: B (that word hurts my ears).
Explanation: ...
