Final answer:
The German Second Army's advance in August 1914 represents a juggernaut, an unstoppable force, making 'b) Juggernaut' the correct term to use. 'Badinage' is inappropriate as it refers to witty banter, not a military entity.
Step-by-step explanation:
On the Western Front in August 1914, the French army prepared itself for the powerful advance of the German Second Army. The correct term to describe this overwhelming military force is juggernaut, which signifies an unstoppable force. Badinage, on the other hand, refers to light-hearted, witty banter and is clearly not fitting in the context of a formidable military assault. Therefore, the correct answer is b) Juggernaut.