Under the IALA-A Buoyage System, when entering from seaward, a buoy indicating the preferred channel is to starboard may have which of the following?

Correct Answer: Option A — square topmark

Under IALA-A guidelines, a preferred channel buoy indicating the main channel to starboard features a red-green-red horizontal band, a conical shape or a square topmark, and a red group flashing light (2+1). Green lights and conical topmarks correspond to the opposite arrangement.