Correct answer:
A. The Declaration of Independence established a new country, while the Declaration of the Rights of Man and of the Citizen only lists a set of principles.
America's Declaration of Independence was establishing the new country's break from Great Britain. In France a little more than a decade later, the Declaration of the Rights of Man and of the Citizen was a statement of principles as representatives of the people were seeking to reform government under the French monarchy.
Additional historical note:
Your question asked about a difference between the documents. There are also key similarities. One important similarity is that both declarations emphasize that persons have natural rights that are to be preserved and protected. The Scientific Revolution had shown that there are natural laws in place in the physical world and in the universe at large. Applying similar principles to matters like government and society, Enlightenment thinkers believed that using reason will guide us to the best ways to operate politically so we can create the most beneficial conditions for society. The declarations at the heart of the American Revolution and French Revolution both emphasized the natural rights of people.