When it is not possible to move forward or change direction or sense of travel, is reversing permitted?

A)No.
B)Yes, but the reversing distance may not exceed 15 metres, nor may it enter a road junction.
C)Yes, but only covering the minimum indispensable distance.Correct
As a general rule, reversing is prohibited, except in the following cases on an exceptional basis and always covering only the minimum indispensable distance:

1. As a complementary manoeuvre to stopping, parking or merging into traffic. In this case the reversing distance may not exceed 15 metres nor may it enter 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, and it may even enter a road junction if necessary.

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