What signal in the International Code of Signals means "I require immediate assistance"?

The signal in the International Code of Signals that signifies "I require immediate assistance" is indeed "CB." This code is recognized internationally and is used in maritime communications to convey urgent requests for help. When this signal is flown or communicated, it alerts nearby vessels and maritime authorities that the sender is in distress and needs immediate support.

Using the correct signal is crucial because effective communication can significantly affect the speed and efficiency with which assistance is provided. Each code in the International Code of Signals serves a unique purpose, and understanding these codes allows mariners to communicate important information succinctly and clearly, especially in emergencies.

In this context, "CB" provides a direct and unequivocal message that action is required, which may not be as clearly conveyed by the other options. The various combinations of letters in the International Code serve different meanings, so recognizing and using the standard codes is essential for safety at sea.