Air enters the lungs during inspiration because

  1. the ribs move down
  2. the volume of the thorax increases and pressure decreases
  3. the diaphragm relaxes
  4. the pressure in the lungs increases
Answer

B) the volume of the thorax increases and pressure decreases

Lower pressure inside draws air in. O Level Biology · Topic 9 Human Gas Exchange · 9.1 Human gas exchange

Biology MCQ · More O Level Biology: Human Gas Exchange MCQs · Practise