The slope of the transitional surface for A, B and C type of runway shall be A. 1 : 5 B. 1 : 7 C. 1 : 10 D. 1 : 12

Option B, 1 : 7, is too steep. This would create a jarring transition for aircraft landing on the runway. Option C, 1 : 10, is too shallow. This would not provide enough of a transition, and aircraft could potentially skid off the runway. Option D, 1 : 12, is also too shallow. For the same reasons as Option C, it would not provide enough of a transition, and aircraft could potentially skid off the runway.