The correct answer is: None of these.
Shunting is the movement of railway vehicles within a railway yard or depot. It is done to assemble or break up trains, to move wagons to and from sidings, and to load and unload wagons. The speed of shunting is typically much slower than the speed of trains on main lines. This is because shunting takes place in confined spaces, and there is a risk of derailment if the wagons are moving too quickly.
The speed of shunting varies depending on the type of railway yard, the type of wagons being shunted, and the experience of the shunter. In general, the speed of shunting is between 5 and 10 kmph.
Option A: 15 kmph is too fast for shunting. This speed is more typical of the speed of trains on main lines.
Option B: 20 kmph is also too fast for shunting. This speed is even more typical of the speed of trains on main lines.
Option C: 10 kmph is a more realistic speed for shunting. This speed is still fast enough to move wagons around, but it is not so fast that there is a risk of derailment.
Option D: None of these is the correct answer.