The correct answer is: A. Decreasing the lever arm
The lever arm is the distance from the point of application of the load to the centroid of the section. The load stress is the force divided by the area of the section. The area of the section is constant, so the load stress can be reduced by decreasing the lever arm.
Option B is incorrect because increasing the total perimeter of bars will increase the area of the section, which will increase the load stress.
Option C is incorrect because replacing larger bars by greater number of small bars will not change the lever arm, and the area of the section will be the same, so the load stress will not change.
Option D is incorrect because replacing smaller bars by greater number of greater bars will increase the lever arm, which will increase the load stress.