Biology 0610 · IGCSE · Gas exchange in humans

Gas exchange in humans — practice question

The stages in expiration are given out of order. 1. Rib cage moves downwards and inwards. 2. Volume of thorax decreases and pressure in lungs increases. 3. Air is pushed out of lungs. 4. Diaphragm and external intercostal muscles relax. Which sequence is the correct one for these stages?

  • A$1 \rightarrow 2 \rightarrow 3 \rightarrow 4$
  • B$1 \rightarrow 4 \rightarrow 2 \rightarrow 3$
  • C$4 \rightarrow 3 \rightarrow 2 \rightarrow 1$
  • D$4 \rightarrow 1 \rightarrow 2 \rightarrow 3$

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