What is the sounding datum used on United States nautical charts?

A. Mean Sea Level (MSL)
✓ Mean Lower Low Water (MLLW)Correct
C. North American Datum of 1983 (NAD 83)
D. Mean Low Water (MLW)

Why B is correct

US charts reference soundings to Mean Lower Low Water (MLLW). The unit of measurement (feet, fathoms, or metres) is stated in the chart title and must be verified before plotting.

Cited:Bowditch Ch. 4 §403

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What is the sounding datum used on United States nautical charts? — USCG Exam Practice · CaptainsGround