To control the silt entry into a distributary at head regulator, King's vanes are provided which are the walls
A
Of R.C.C. or steel plate 8 cm thick
B
Of height $${\frac{1}{3}^{{\text{rd}}}}$$ to $${\frac{1}{4}^{{\text{th}}}}$$ the depth of water in the main canal
C
Spaced at interval of $$1\frac{1}{2}$$ times their heights
D
All the above
Correct Answer: All the above