The right lymphatic duct is the correct answer because it is one of the main lymphatic vessels in the body. It drains lymph from the right side of the head, neck, and upper limb, and empties into the right subclavian vein. The other options, such as the thymus, lymphatic vessels, thoracic duct, and spleen, are all parts of the lymphatic system but are not specifically the correct answer in this context.