What is the term for the system where each branch of government is able to check, or limit, the power of the other two branches

The term is "Checks and Balances", it refers to the three branches and how they check on each other so that they don't have to much power.

C. There is a conflict between Native Americans and the settlers.

Explanation:

In these lines, Jefferson urges the Native American people to work on establishing peaceful relationships with the white settlers. Jefferson says that all people will benefit from such a peace, and he advocates for this while trying not to listen "to wicked men, who may try to make us enemies." This statement, along with the image of war, suggests that conflicts do arise between these two groups, and that this is the reason why Jefferson is advocating for peace.