Final answer:
Governments and populations were unprepared for the prolonged and extensive nature of World War 1.
Step-by-step explanation:
The correct option is A. Governments and populations were unprepared for the war's length and extent. The onset of World War 1 caught many governments and populations off guard, as they were unprepared for the prolonged and extensive nature of the conflict.
At the time, there had been little experience of war on European soil for over 40 years, and the previous conflicts were relatively short and less bloody. This lack of recent experience and understanding of the changing nature of warfare contributed to the unpreparedness.
Furthermore, the expectation was that the war would be quick and decisive. Many people believed that the war would resolve nationalistic rivalries and be over by Christmas, as evidenced by the enthusiastic response to the start of the war and the high number of voluntary enlistments.