During Thick or Foggy weather, 2 Detonators must be placed in rear of Engineering indicator at A. 270 meters B. 90 meters C. 400 meters D. None of these

The correct answer is: A. 270 meters.

During thick or foggy weather, 2 detonators must be placed in rear of Engineering indicator at 270 meters. This is to ensure that the train will stop in time if it cannot see the signal.

Option B is incorrect because it is the distance between the detonators when the weather is clear.

Option C is incorrect because it is the distance between the detonators when the weather is foggy.

Option D is incorrect because it is not a valid option.