The correct answer is: A. 1 minute of latitude.
A nautical mile is a unit of length equal to one minute of arc along a great circle of the Earth, which is 1.852 kilometers (1.150778 miles). It is used in navigation, especially maritime navigation, and is also used as a unit of speed.
A minute of latitude is one sixtieth of a degree of latitude. The Earth’s circumference is 40,075 kilometers (24,901 miles) at the equator, so one degree of latitude is 111.3 kilometers (69.1 miles). One minute of latitude is therefore 1.852 kilometers (1.150778 miles).
A minute of longitude is one sixtieth of a degree of longitude. The Earth’s circumference is 40,075 kilometers (24,901 miles) at the equator, so one degree of longitude is 111.3 kilometers (69.1 miles). One minute of longitude is therefore 1.852 kilometers (1.150778 miles) at the equator, but it is less at higher latitudes because the Earth is not a perfect sphere.
Therefore, the nautical mile is the length of 1 minute of latitude, not 1 minute of longitude.