Answer:
B. The long supply line from Britain could not be sustained
The British army was arguably the best in the world at that time. It was an extremely well-disciplined and trained force. They were well paid and well trained. But a major weakness was that in order to supply new troops, supplies for the war and soldiers like food and guns it needed to travel across the Atlantic ocean. This is extremely costly and needs a long time to arrive where it was most needed.