Maximum impact speed when shunting a group of roller bearing fitted stock coupled together must be? A. 2 kmph B. 2.5 kmph C. 3 kmph D. 3.5 kmph

Option A is incorrect because it is too low. The wagons may not be able to couple properly if the impact speed is too low.

Option C is incorrect because it is too high. The wagons may derail if the impact speed is too high.

Option D is incorrect because it is not a valid option.