What type of navigation line is often used for long-distance ocean travel?

The great circle is the correct answer because it represents the shortest distance between two points on the surface of a sphere, which makes it extremely effective for long-distance ocean travel. When navigating across vast expanses of water, using a great circle route allows vessels to minimize fuel consumption and travel time by taking advantage of the Earth's curvature.

In practical terms, navigators chart a course that follows the arc of a great circle, which may appear curved on a standard map projection, but efficiently connects two distant points. This type of navigation is fundamental for intercontinental shipping and aviation, where distances are significant and efficiency is essential.

In contrast, other navigation lines like the straight line do not account for the Earth's curvature and therefore may not represent the actual shortest path over long distances. Rhumb lines, while easier to plot because they maintain a constant compass heading, do not provide the efficient path that great circles do for long travel distances. Curved paths could refer to various navigational approaches but lack the specificity and practicality of great circles in ocean navigation.