Which sign is used to indicate the end of a block?

Answer: B — An End of Block sign

The End of Block sign is specifically designed to denote the conclusion of a block section on a railway system. This sign provides clear and direct communication to train operators and personnel regarding the limit of a defined block where specific operating rules and safety measures apply. Understanding where each block begins and ends is critical for maintaining safety, ensuring proper signal indications, and coordinating train movements effectively. While other signs serve important functions within railway operations, such as the Block Limit sign indicating where a block begins, or an Approach Sign which informs the train of an upcoming signal, they do not serve the specific function of marking the termination of a block. The Working Limits Stop Sign is utilized for different scenarios concerning maintenance and work zones rather than indicating block boundaries. Thus, the End of Block sign is the correct and most precise choice for indicating the end of a block in train operations.