The graph shows the volume of a subject’s lungs measured over a period of 40 seconds.

Determine the total volume of air breathed in during the 40 seconds (give your answer to the nearest 0.25dm3).

**A. 7.75 dm3**

B. 8 dm3

C. 8.5 dm3

D. 8.75 dm3

E. 9.10 dm3

How to interpret this type of graphs?