The correct answer is C) dead-reckoning position. A dead-reckoning position is obtained solely by applying a vessel's course and speed to a known starting position, without any additional navigational information. This is in contrast to a fix, which is a precise position determined using external references such as visual bearings, electronic positioning systems, or celestial observations. The other options are incorrect because: A) a running fix involves using multiple position lines to determine a more accurate position, B) a probable position is an estimated location based on multiple sources of information, and D) a fix is the most accurate position determination method, not a dead-reckoning position.