O-LevelBiologyRespiration5090/12 · Oct/Nov 2021 · Q171 Mark

Which statements about gaseous exchange in the alveoli are correct? 1 The alveolus wall is one cell thick. 2 Carbon dioxide can diffuse through the alveolus wall. 3 Oxygen dissolves in moisture on the surface of the alveolus before diffusing into the blood.

A1 and 2 only

B1 and 3 only

C2 and 3 only

D1, 2 and 3

✓ Correct answer

D: 1, 2 and 3

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Topic: Respiration, O-Level Biology (syllabus 5090). Multiple choice, 1 mark.
Source: O-Level Biology, Oct/Nov 2021 Paper 1 Variant 2, question 17.

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