ANS:D -

To ensure that the pressure beneath the base of a retaining wall is wholly compressive (i.e., there is no tension), the resultant of the weight of the wall and the pressure exerted by the retained earth should be located within the middle third of the base width b. This ensures that the resultant force falls within the middle third of the base width and avoids tension within the base. The permissible eccentricity (distance from the center of the base to the line of action of the resultant force) is typically specified as one-third of the base width (b/3​). So, the eccentricity should not be more than one-third of the base width, or b/3​, to prevent tension in the base of the retaining wall.