The correct answer is: A. less
Stopping sight distance is the distance a driver needs to see and react to an obstacle in front of them and stop safely. On a descending gradient, the stopping sight distance is less than on a level surface because the vehicle will be traveling faster. This means that the driver will have less time to react and stop.
Option B is incorrect because the stopping sight distance is actually less on a descending gradient. Option C is incorrect because the stopping sight distance is not the same on a descending gradient as on a level surface. Option D is incorrect because the stopping sight distance is not dependent on the speed on a level surface, but it is dependent on the speed on a descending gradient.