In the image, what does "B" represent?

a. Expiratory valve line
b. Exhalation valve
c. Expiratory line
d. Main inspiratory line

ANS: C
The external exhalation valve is represented by the letter "C" in the figure. "B" is pointing to the expiratory line. The main inspiratory line is represented by the letter "A." The expiratory valve line is represented by "D."