Pick up the incorrect statement from the following

A. Side walls of a venturi head flume are splayed out from the end of the throat at 1 : 10 for a length of 4.5 m

B. Length of side walls should be such that the width of the flume is made equal to $${\frac{2}{3}^{{\text{rd}}}}$$ the bed width of the distributary

C. Once the width of the flume becomes $${\frac{2}{3}^{{\text{rd}}}}$$ of the width of the distributary, the splayed walls are increased to 1 in 3 to get full bed width

D. None of these

Answer: Option D