Where should the registration numbers be displayed on a vessel capable of planing?

The correct choice is that registration numbers should be displayed on both sides of the vessel. This requirement is in place to ensure clear visibility from multiple angles, which is essential for identification by authorities and other vessels. The registration numbers help in monitoring and enforcing maritime laws, and displaying them on both sides maximizes the chances that the numbers can be seen by others on the water, regardless of which direction they approach from.

While displaying numbers on the stern alone might allow for identification from behind, it fails to meet the needs for visibility when vessels are approaching from the sides. Placing numbers on the bow also does not provide sufficient visibility, as the bow may not always be visible to other vessels or authorities in all situations. Similarly, displaying numbers on the top of the cabin would restrict visibility to those who are directly above, which is not practical or effective for the purpose of vessel identification.