Biology 5090 · O Level · Human gas exchange

Human gas exchange — practice question

Each of the students was given the apparatus shown. They put the mouthpieces into their mouths and then gently breathed in and out through the apparatus ten times. Which statement describes what occurred as they breathed in and out?

  • AWhen they breathed in, air from the room bubbled through test-tube U and the limewater became cloudy in test-tube U.
  • BWhen they breathed out, air from their lungs bubbled through test-tube T and the limewater became cloudy in test-tube T.
  • CWhen they breathed in, air from the room bubbled through test-tube T and the limewater remained clear in test-tube T.
  • DWhen they breathed out, air from their lungs bubbled through test-tube U and the limewater remained clear in test-tube U.

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