If q is the average sewage flow from a city of population P, the maximum sewage flow

A. $${\text{Q}} = \left( {\frac{{4 + \sqrt {\text{P}} }}{{18 + \sqrt {\text{P}} }}} \right){\text{q}}$$

B. $${\text{Q}} = \left( {\frac{{18 + {\text{P}}}}{{4 + \sqrt {\text{P}} }}} \right){\text{q}}$$

C. $${\text{Q}} = \left( {\frac{{18 + \sqrt {\text{P}} }}{{4 + \sqrt {\text{P}} }}} \right){\text{q}}$$

D. $${\text{Q}} = \left( {\frac{{5 + \sqrt {\text{P}} }}{{15 + \sqrt {\text{P}} }}} \right){\text{q}}$$

Answer: Option C