The discharge (Q) through an orifice meter is given by __________:(Where a1 and a2 are the areas of the pipe and orifice, Cd is the coefficient of discharge and h is the difference of pressure head in the orifice meter)

• A. \(Q = {C_d}\frac{{{a_1} - {a_2}}}{{\sqrt {a_1^2 - a_2^2} }}\sqrt {2gh} \)
• B. \(Q = {C_d}\frac{{{a_1}/{a_2}}}{{\sqrt {a_1^2 - a_2^2} }}\sqrt {2gh} \)
• C. \(Q = {C_d}\frac{{{a_1} + {a_2}}}{{\sqrt {a_1^2 - a_2^2} }}\sqrt {2gh} \)
• D. \(Q = {C_d}\frac{{{a_1}{a_2}}}{{\sqrt {a_1^2 - a_2^2} }}\sqrt {2gh} \)