A. Lower end of ventilating column
B. Upper end of ventilating column
C. Upper end of the manhole
D. First step in manhole
Correct Answer: Upper end of ventilating column ✔
Last Updated: August 25, 2020
A. Lower end of ventilating column
B. Upper end of ventilating column
C. Upper end of the manhole
D. First step in manhole
Correct Answer: Upper end of ventilating column ✔
Last Updated: August 25, 2020