The correct answer is: A. 00000-0
In case of defective head light, the bell code given on block instrument to the station in advance is 00000-0. This code indicates that the train is approaching the station with a defective head light. The station staff will then be prepared to take appropriate action, such as stopping the train or providing a replacement light.
The other options are incorrect because they do not correspond to the correct bell code for a defective head light. Option B, 000000-0, is the bell code for a defective tail light. Option C, 000000-000, is the bell code for a defective brake. Option D, 0000-00, is the bell code for a train approaching the station without a flagman.
I hope this helps! Let me know if you have any other questions.