The most economical section of a trapezoidal channel is one which has hydraulic mean depth
equal to
(A) 1/2 × depth
(B) 1/2 × breadth
(C) 1/2 × sloping side
(D) 1/4 × (depth + breadth)
equal to
(A) 1/2 × depth
(B) 1/2 × breadth
(C) 1/2 × sloping side
(D) 1/4 × (depth + breadth)