The reversing manoeuvre is totally prohibited on...

A)the carriageway of any road.
B)roads reserved for motor vehicles.
C)motorways and dual carriageways.Correct
As a general rule, reversing is prohibited, except in the following cases exceptionally and always covering the minimum indispensable distance:

1. As a complementary manoeuvre to stopping, parking or joining traffic. In this case the reversing distance may not exceed 15 metres nor encroach on a road junction.
2. When it is not possible to move forward or change direction or sense of travel. In this case there is no limit on the reversing distance, even being able to encroach on a road junction if necessary.

On motorways and dual carriageways it is totally prohibited:
- Changing the direction of travel, except at places designated for that purpose.
- Reversing.
- Entering the central reservation or its transverse crossings.