To carry out a stop, is it permitted to reverse?

A)No.
B)Yes, always.
C)Yes, under certain conditions.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 for stopping, parking, or joining the flow of traffic. In this case, the reversing distance may not exceed 15 metres or encroach upon an intersection.
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 upon an intersection if necessary.
The reversing manoeuvre is prohibited on dual carriageways and motorways.