Please choose the correct answer to the question: A science teacher filled one balloon with helium gas and a second balloon with carbon dioxide. The helium-filled balloon rose to the ceiling, and the balloon filled with carbon dioxide fell to the floor. Which statement is an inference based on this demonstration?

Answer1: Each balloon behaved differently. Answer2: Helium gas has a lower density than air. Answer3: Carbon dioxide causes a balloon to expand. Answer4: Balloons can be filled with different gases.

Answer format: answer1/answer2/answer3/answer4