The differential equation of the gradually varied flow can be written by using Manning’s Formulafor the case off a wide rectangular channel as (dy/dx) =

• A. s0{[1-(yn/y)3.33]/[1-(yn/y)3]}
• B. s0{[1-(yc/y)3.33]/[1-(yc/y)3]}
• C. s0{[1-(yn/y)3]/[1-(yn/y)3]}
• D. s0{[1-(yo/yc)3]/[1-(yn/y)3.33]}