The correct answer is: A. 20 kmph.
A train running through from station without brake van provided with Tail lamp must run at a speed of not more than 20 kmph. This is to ensure the safety of the train and the people on board. If the train runs at a higher speed, it may not be able to stop in time if there is an emergency.
The other options are incorrect because they do not meet the safety requirements for a train running through from station without brake van provided with Tail lamp.
Option B: Stop & Start is not a safe speed for a train to run at. If the train stops and starts frequently, it may be difficult for the passengers to keep their balance and may cause injuries.
Option C: 15 kmph is a safe speed for a train to run at, but it is not the minimum speed required for a train to run through from station without brake van provided with Tail lamp.
Option D: Normal speed is not a specific speed. It can vary depending on the type of train, the track conditions, and the weather conditions. Therefore, it is not a safe speed for a train to run through from station without brake van provided with Tail lamp.