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A balloon filled with hydrogen gas rises in the air because:

AHydrogen is very light
BThe weight of the balloon is less than the upthrust of the air
CGravity does not act on hydrogen
DHydrogen reacts with air

✓ Correct Answer: BThe weight of the balloon is less than the upthrust of the air

A balloon rises when the upthrust (weight of the air displaced) is greater than the total weight of the balloon and gas.

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