A singly reinforced beam has breadth b, effective depth d, depth of neutral axis n and critical neutral axis n1. If fc and ft are permissible compressive and tensile stresses, the moment to resistance of the beam, is____________________?
A. bn (fc/2) (d – n/3)
B. Atft (d – n/3)
C. ½ n1 (1 – n1/3) cbd²
D. All the above