The correct answer is C) amount of helm carried for a steady course. When being relieved at the helm, the new helmsman would find it handy to know the amount of helm (rudder angle) being used to maintain a steady course. This information allows the new helmsman to more easily take over and continue steering the vessel on the same heading. The amount of helm provides a reference point for the new helmsman to make any necessary adjustments. The other options are not as directly relevant to the task of taking over the helm. Leeway (A) and variation (D) are more general navigational considerations, while deviation (B) is specific to magnetic compass errors, which may not be immediately relevant to the helmsman's duties.