A rotary current sets through all directions of the compass. The time it takes to complete one of these cycles, in a locale off the East coast of the US, is approximately __________.

Correct Answer: Option D — 12 1/2 hours

Rotary currents, characteristic of offshore waters, complete a full 360-degree directional cycle in approximately 12.5 hours, corresponding directly to the semi-diurnal lunar tidal cycle.