Speed of train when whistle becomes defective is ________ km/h. A. 30/8 B. 25/8 C. 45/8 D. 40/8

The correct answer is $\boxed{\text{B) 25/8 km/h}}$.

The speed of the train is not affected by the whistle becoming defective. The whistle is used to warn people of the train’s approach, but it does not affect the train’s speed.

Option A is incorrect because it is the speed of the train when the whistle is working. Option C is incorrect because it is the speed of the train when the whistle is blowing. Option D is incorrect because it is the speed of the train when the whistle is not working and not blowing.