What must a train do when faced with a block limit signal?

When a train encounters a block limit signal, it must adhere to the rules regarding signal indications, which are critical for maintaining safe train operations on the railway. The correct response involves understanding that a block limit signal indicates specific operational instructions that must be followed.

In this context, if the signal is clear, the train can proceed under the assumption that it has the right to continue safely. Clear signals represent an indication that the track ahead is clear and available for use, therefore allowing the train to operate with confidence.

Following this interpretation, if the signal shows clear, the train is permitted to proceed as if a clear signal is displayed, ensuring that the safety protocols are maintained. The understanding of signal status and adherence to instructions is vital in preventing accidents and ensuring smooth operations within the rail network.

Other options imply actions that could interfere with safety protocols, such as waiting unnecessarily when it's safe to proceed or passing a signal without thorough verification, which could lead to potential collisions or violations of operational procedures.