The correct answer is: A. 8 km/h.
Non-interlocked points are railway points that are not controlled by a signal. This means that the driver of the train is responsible for ensuring that the points are set correctly before passing through them. If the points are not set correctly, the train could derail.
To reduce the risk of derailment, the maximum speed of a train passing through a non-interlocked point is 8 km/h. This speed limit is designed to give the driver enough time to stop the train if the points are not set correctly.
Option B, 10 km/h, is too fast. At this speed, the driver would not have enough time to stop the train if the points are not set correctly.
Option C, 15 km/h, is also too fast. At this speed, the driver would have a very small margin of error if the points are not set correctly.
Option D, 20 km/h, is much too fast. At this speed, the driver would almost certainly derail the train if the points are not set correctly.