The slope of the obstruction clearance line from the boundary of the heliport should be A. 1 : 2 B. 1 : 5 C. 1 : 8 D. 1 : 40

Option B is incorrect because the slope is too steep. This would make it difficult for helicopters to land and take off safely.

Option C is incorrect because the slope is too shallow. This would not provide enough clearance for helicopters to land and take off safely.

Option D is incorrect because the slope is not a standard slope for obstruction clearance lines.