The correct answer is C. 0.3 N/mm2 to 0.7 N/mm2.
The permissible diagonal tensile stress in reinforced brick work is the maximum tensile stress that can be applied to a brick wall before it fails. This value is typically between 0.3 N/mm2 and 0.7 N/mm2, depending on the type of brick and the construction method used.
Option A is incorrect because the permissible diagonal tensile stress in reinforced brick work is much higher than 0.1 N/mm2.
Option B is incorrect because the permissible diagonal tensile stress in reinforced brick work is not zero.
Option D is incorrect because the permissible diagonal tensile stress in reinforced brick work is not about 1.0 N/mm2.