Mean high water is the reference datum used to measure __________.

Correct Answer: Option C — heights of topographical features in the United States

In the United States, nautical charts use Mean High Water (MHW) as the reference datum for the heights of topographical features, such as bridge clearances and shoreline elevations. This standard ensures consistency for mariners when calculating vertical clearance under structures, as defined by the National Ocean Service and NOAA charting standards.