The correct answer is D. 10 kmph.
In Automatic areas when there are no signals and communication, the speed of the train is limited to 10 kmph while working on T/B 912 during day. This is to ensure the safety of the train and its passengers.
Option A is incorrect because the speed limit is 10 kmph, not 25 kmph.
Option B is incorrect because the speed limit is 10 kmph, not 20 kmph.
Option C is incorrect because the speed limit is 10 kmph, not 15 kmph.