Final answer:
The proceed hand signal on a railroad should never be given with a red lantern, as red signifies 'stop' or 'proceed with caution' and is a universal warning symbol.
Step-by-step explanation:
The question relates to the use of hand signals in railroad operations, where different lantern colors and movements have specific meanings for the safety of train movements.
The sentence to complete is: A proceed hand signal may never be given with a red lantern. In the context of railroad signaling, a red light or lantern usually signifies 'stop' or 'proceed with caution' and is the universal symbol for danger. Therefore, it should not be used to give a proceed signal, which is commonly associated with green or white lights.