A retaining wall of trapezoidal section having base which ‘b’ retains earth at its back. For no tension to be developed at base, the resultant force will intersect the base from
centre line of the line, within a distance of

A

$$\frac{b}{3}$$

B

$$\frac{b}{4}$$

C

$$\frac{b}{5}$$

D

$$\frac{b}{6}$$