The detention time of a circular tank of diameter d and water depth H, for receiving the sewage Q per hour, is

A. $$\frac{{{{\text{d}}^2}\left( {0.011{\text{d}} + 0.785{\text{H}}} \right)}}{{\text{Q}}}$$

B. $$\frac{{{\text{d}}\left( {0.022{\text{d}} + 0.085{\text{H}}} \right)}}{{\text{Q}}}$$

C. $$\frac{{{\text{d}}\left( {0.785{\text{d}} + 0.011{\text{H}}} \right)}}{{\text{Q}}}$$

D. $$\frac{{{\text{d}}\left( {0.285{\text{d}} + 0.011{\text{H}}} \right)}}{{\text{Q}}}$$

Answer: Option A