Multiple choice

Balloons are filled with _________.

  1. oxygen

  2. hydrogen

  3. nitrogen

  4. none of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Hydrogen gas is the lightest gas and was historically used to fill balloons because it provides good lift. However, hydrogen is highly flammable, which is why modern balloons typically use helium instead. Among the given options, hydrogen is the correct answer for traditional balloon-filling gas.

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