Here's a problem to solve: 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?

Among the 4 following options, which is the correct answer?

- A: Each balloon behaved differently.
 
- B: Helium gas has a lower density than air.
 
- C: Carbon dioxide causes a balloon to expand.
 
- D: Balloons can be filled with different gases.
 