NAVIGATION — Choose the correct application of the unit. Question: A nautical mile is a unit of distance primarily used in which domain?

Introduction / Context:
Nautical miles are fundamental in marine and air navigation. This unit ties distance directly to Earth’s geometry, simplifying charting and position calculations on a spherical surface.

Given Data / Assumptions:

• 1 nautical mile (nmi) is defined as exactly 1852 m.
• It relates closely to latitude: 1 minute of arc along a meridian ≈ 1 nmi.
• Used with knots for speed (nautical miles per hour).

Concept / Approach:
Because route planning over Earth’s surface uses angular coordinates, a distance unit tied to arcminutes is convenient for sailors and pilots. Road transport uses statute miles or kilometres; astronomy uses parsecs/AU/light-years; boundary measurement is a legal process not tied to this unit.

Step-by-Step Solution:
Recall definition: 1 nmi = 1852 m.Note usage: marine and aviation navigation charts.Match domain: navigation is the primary application.Exclude domains using statute miles/km or astronomical units.

Verification / Alternative check:
Speed in navigation is “knots,” where 1 knot = 1 nmi/h, reinforcing that the unit belongs to navigation practice.

Why Other Options Are Wrong:
B) Road mile refers to statute mile ≈ 1609 m, not nautical mile.C) Astronomy uses AU, ly, or parsec.D) National boundaries are surveyed in various units, commonly km.E) City maps use km or metres for fine scale.

Common Pitfalls:
Equating all “miles.” Nautical mile is longer than the statute mile and is specialized for navigation.

Final Answer:
navigation