What must occur if a conflicting movement is stopped by the control operator?

The correct answer highlights the procedure that allows for safe operations after a conflicting movement has been halted by the control operator. When a conflicting movement is stopped, it creates a window of opportunity for the controlled movement of other trains. Specifically, if the control operator deems it safe and issues an authorization, another train may indeed be allowed to proceed. This ensures that traffic flow can continue and that efficiency is maintained while still adhering to the necessary safety protocols. It implies the importance of communication and coordination among crew members and control operators to manage train movements effectively.

Contextually, the other responses do not align with safe operational practices. Replacing a signal or requiring the stopped train to move immediately could compromise safety protocols, as the crew needs to assess the situation fully before making any moves. Meanwhile, the control operator leaving their post would likely disrupt the control of train movements, further increasing the risk of accidents or miscommunication. Thus, allowing another train to proceed under the right circumstances is the most appropriate and safe action in this scenario.