ANS:D - all of these.

The rise and fall method of reduction of levels provides a check on all of these: back sights, fore sights, and intermediate sights. The rise and fall method ensures that the arithmetic sum of the rises and falls from backsight to foresight matches the actual difference in elevation between the starting and ending points. This helps to verify the accuracy of the leveling process and ensures that errors are minimized or detected during the surveying operation.