The correct answer is: D. None of these
The flow velocity in detritus tanks is typically between 0.05 and 0.15 m/sec. This is because detritus tanks are designed to remove suspended solids from wastewater, and a higher flow velocity would result in the solids being carried out of the tank without being removed.
Option A: 0.05 m/sec is a possible flow velocity in detritus tanks. However, it is on the lower end of the range, and it is more likely that the flow velocity would be closer to 0.15 m/sec.
Option B: 0.09 m/sec is also a possible flow velocity in detritus tanks. However, it is on the higher end of the range, and it is more likely that the flow velocity would be closer to 0.15 m/sec.
Option C: 1.25 m/sec is too high a flow velocity for a detritus tank. This is because a higher flow velocity would result in the solids being carried out of the tank without being removed.