Which of these indicates a preferred channel having a lateral mark?

The identification of a preferred channel having a lateral mark is governed by the IALA (International Association of Lighthouse Authorities) buoyage system, which uses distinct color schemes and symbols to convey navigational information to mariners. In this system, the top color of a lateral mark is specifically designated to indicate the channel's preference.

For instance, in many regions, a mark with a green top signifies that this is a preferred channel to starboard when navigating inward, while a mark with a red top indicates a preferred channel to port. This rule helps in guiding vessels safely through navigable waters by clearly marking the path they should follow.

The other choices, while relevant to maritime buoys and aids to navigation, do not serve the same specific function in representing a preferred channel. The light color, bottom color of the mark, and topmark can convey various types of information but lack the direct link to indicating channel preference that the top color provides. Therefore, the top color of the mark is a key element in determining the preferred route within a waterway system.