Under the IALA-A Buoyage System, when entering from seaward, a buoy indicating the preferred channel is to starboard may have a __________.

Correct Answer: Option B — square topmark

Under IALA-A, a preferred-channel-to-starboard buoy is red with a green horizontal band. The topmark for this buoy is a red cylinder. Conversely, a preferred-channel-to-port buoy is green with a red band and features a square topmark. These shapes provide visual identification even when the light is not visible.