The main idea doesn't explain in detail why it is the main idea. It doesn't prove that it is the main idea, it only states so.
The first option is correct
Answer:
Keep your thoughts positive because your thought become YOUR WORDS. Keep your words positive because your words become YOUR BEHAVIOR. Keep your behavior positive because your behavior becomes YOUR HABITS.
Explanation:
This is a very famous quote from Mahatma Ghandi.
Hope this helps!
:)
