In the case of panel wall subjected to horizontal loads at right angles to the plane of the wall, with the mortar not leaner than Ml type, tensile stress in bending in the vertical direction may be allowed to the extent of _______________?
A. 0.4 kg/cm2
B. 0.7 kg/cm2
C. 1.0 kg/cm2
D. 1.2 kg/cm2