What is the most likely reason Churchill regularly brings up negative details
about the war, such as the German victory in the Battle of France?

Explanation:

I think the most likely reason Churchill regularly brougth up negative details about the war is: A. He wants Britain to have realistic expectations about the future. As a great strategist, Churchill focused on the evidence given by other battles, like the German victory in France, to learn from his enemy.

c) troops march forward in close formation against newer, more accurate weapons