The correct answer is C) The drift of the current should be averaged out on a one hour basis. This is because the drift of the current is variable and can change over time, so averaging it out over a one hour period provides a more accurate representation of the current's effect on the vessel's position. Averaging the current drift over time helps to smooth out any short-term fluctuations and gives a more reliable estimate for navigation purposes. The other options are incorrect because: A) Measuring the distance between simultaneous EP and DR positions cannot determine the current, as the DR position does not account for current. B) The distance between a simultaneous DR position and fix is not equal to the drift of the current, as the fix incorporates the effect of the current. D) The current should be used for further plotting, as it is a known variable that affects the vessel's position.