Quantity of fresh air required for a man is 1000 cubic feet of air for every____________?
A. 5 minutes
B. 10 minutes
C. 15 minutes
D. 20 minutes
Quantity of fresh air required for a man is 1000 cubic feet of air for every____________?
A. 5 minutes
B. 10 minutes
C. 15 minutes
D. 20 minutes