The most economical section of a trapezoidal channel is one which has hydrulic mean depth equal to:

A

$$\frac{1}{2}$$ depth

B

$$\frac{1}{2}$$ breadth

C

$$\frac{1}{2} \times$$ depth $$\times$$ breadth

D

$$\frac{1}{2}$$(depth and breadth)