Caution and Termination indication Boards will be fixed from the bridge or vulnerable places at A. 400 meters B. 600 meters C. 1000 meters D. None of these

The correct answer is: A. 400 meters.

Caution and Termination indication Boards will be fixed from the bridge or vulnerable places at 400 meters. This is to ensure that drivers have enough time to slow down and stop before reaching the bridge or vulnerable place.

Option B is incorrect because it is too far. Drivers would not have enough time to slow down and stop before reaching the bridge or vulnerable place.

Option C is incorrect because it is too close. Drivers would not have enough time to react if something happened at the bridge or vulnerable place.

Option D is incorrect because it is not a specific distance.