The diameter (d) of a nozzle fixed at the end of a pipe (diameter D, length L) for maximum energy, is

• A. <img src="/_files/images/civil-engineering/hydraulics/154-7.176-1.png">
• B. <img src="/_files/images/civil-engineering/hydraulics/154-7.176-2.png">
• C. <img src="/_files/images/civil-engineering/hydraulics/154-7.176-3.png">
• D. <img src="/_files/images/civil-engineering/hydraulics/154-7.176-4.png">