Permissible velocity of water flowing through concrete lined tunnel is usually __________________?
A. 3 – 4m/sec
B. 4 – 5m/sec
C. 5 – 6m/sec
D. 6 – 7m/sec
A. 3 – 4m/sec
B. 4 – 5m/sec
C. 5 – 6m/sec
D. 6 – 7m/sec