Critical depth (h) of a channel, is

• A. <img src="/_files/images/civil-engineering/hydraulics/155-7.188-1.png">
• B. <img src="/_files/images/civil-engineering/hydraulics/155-7.188-2.png">
• C. <img src="/_files/images/civil-engineering/hydraulics/155-7.188-3.png">
• D. <img src="/_files/images/civil-engineering/hydraulics/155-7.188-4.png">