The observation that most accurately reflects the benefits of using the Mercator projection over a Mollweide projection is:
"Because the Mercator projection preserves the accuracy of directions, it can be used for navigation."
The Mercator projection is particularly useful for navigation because it keeps angles true, making it easier for navigators to plot straight-line courses. In contrast, the Mollweide projection, while it provides a more accurate representation of area, distorts shape and angles, making it less suitable for navigation.