The correct answer is C. 6 km/h.
Shunting is the movement of railway vehicles within a yard or depot, or to and from a siding. It is usually done at low speed, and the wagons are often pushed or pulled by a shunting locomotive.
The speed of shunting is typically limited by the need to avoid damage to the wagons or the track. It is also important to ensure that the wagons do not derail.
In general, the speed of shunting is between 2 and 10 km/h. However, the exact speed may vary depending on the type of wagons, the condition of the track, and the experience of the shunter.
In the case of 5 box wagons, the shunting speed is typically around 6 km/h. This is a safe and efficient speed for moving the wagons around a yard or depot.
Option A is incorrect because it is too low. The speed of shunting is typically not less than 2 km/h.
Option B is incorrect because it is too high. The speed of shunting is typically not more than 10 km/h.
Option D is incorrect because it is not a realistic speed for shunting 5 box wagons.