This diagram was drawn from a section showing part of an alveolus and a red blood cell in a capillary. The magnification of the drawing is $\times 5000$. What is the shortest distance that oxygen has to diffuse from the air in an alveolus into the red blood cell?
- A$0.1\,\text{nm}$
- B$1.0\,\text{nm}$
- C$0.1\,\mu\text{m}$
- D$1.0\,\mu\text{m}$