Biology 0610 · IGCSE · Gas exchange in humans

Gas exchange in humans — practice question

When we breathe out, ......1...... is ......2...... through the lungs. Which words correctly fill gaps $1$ and $2$?

  • Acarbon dioxide; excreted
  • Bcarbon dioxide; respired
  • Coxygen; excreted
  • Doxygen; respired

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