Question

what gas is used to fill the balloons so they can fly?
o oxygen
o helium
o hydrogen
o nitrogen

Explanation:

To determine the gas for flying balloons, we analyze the density and safety:

• Oxygen ($\ce{O2}$) and Nitrogen ($\ce{N2}$) have densities close to air, so they don’t lift balloons.
• Hydrogen ($\ce{H2}$) is flammable and unsafe for consumer balloons.
• Helium ($\ce{He}$) is non - flammable, less dense than air, and commonly used for floating balloons.

Answer:

B. Helium