This sentence is from the passage. "It keeps us and all of the objects around us fixed to the earth's surface; it keeps the air we breathe from escaping to outer space; it keeps the moon in orbit around the earth and it keeps the earth bound in orbit around the sun." (Paragraph 2) How does the sentence help develop an important idea about gravity?
1. The sentence corrects a misunderstanding about the effect of gravity on air.

2. The sentence reveals the difficulty of 2 determining how gravity works in space.

3. The sentence explains the role that distance, between objects plays in gravity's strength.

4. The sentence emphasizes that gravity has an influence both on our planet and beyond it.