As a general rule, on which roads is it prohibited to reverse?

A)Only on urban roads.
B)Only on motorways and dual carriageways.
C)On all roads, except as a complement to certain manoeuvres.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 merging into traffic. In this case the reversing distance must not exceed 15 metres nor encroach upon a road junction.
2. When it is not possible to move forward or to change direction or sense of travel. In this case there is no limit on the reversing distance, and it may even encroach upon a road junction if necessary.

Reversing is prohibited on dual carriageways and motorways.