Final answer:
A green can buoy marks the right (starboard) side of the channel when a boat is entering from the open sea or heading upstream.
Step-by-step explanation:
A green can buoy marks the edge of the channel on a boater's right (starboard) side when entering from the open sea or heading upstream. The correct answer is B) Right (starboard). In nautical terms, 'starboard' refers to the right side of a vessel, while 'port' refers to the left side when facing forward toward the bow (front) of the boat. This navigation rule helps boaters determine their position in relation to the channel and avoid potential hazards when navigating waterways.