The correct answer is A. 10 kmph.
When passing through a station during the day, the train must slow down to 10 kmph if it is running without a brakevan and tail board. This is to ensure the safety of passengers and other people on the platform.
Option B, 20 kmph, is too fast and could result in an accident. Option C, 25 kmph, is also too fast and could result in an accident. Option D, normal speed, is not specific enough. It is important to slow down to 10 kmph when passing through a station during the day, regardless of the train’s normal speed.