Final answer:
The action of Napoleon's that caused the greatest human losses was B. The invasion of Russia. This disastrous military campaign led to severe human losses and marked a turning point in Napoleon's fortunes. Other actions, though significant, did not result in the same level of human loss.
Step-by-step explanation:
The action of Napoleon's that caused the greatest human losses was indeed B. The invasion of Russia, done as part of Napoleon's attempts to dominate Europe. This disastrous military campaign led to severe losses. Although other actions, such as A. The Battle of Trafalgar, C. The sale of the Louisiana Territory, and D. The Peninsular War, also played significant roles in his reign, they did not result in the same level of human losses as the invasion of Russia.
The Russian campaign was a strategic failure for Napoleon's Grand Army. It started with a force of 680,000 and returned with just 27,000, largely due to the harsh Russian winter and attrition from fighting. The failure of this invasion marked a turning point in Napoleon's fortunes.
In contrast, while events such as the Peninsular War and the Battle of Trafalgar posed significant challenges to Napoleon's reign, they were not as devastating in terms of human losses. The sale of the Louisiana Territory, although a significant geopolitical event, was primarily a financial transaction, not a military action, thus did not involve human losses in the same way.
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