Final answer:
The main reason for creating three branches of government is to prevent any one branch from gaining too much power, ensuring a balance and separation of powers within the government.
Step-by-step explanation:
The primary purpose of establishing three branches of government is B) Preventing any part of government from having too much power. The U.S. Constitution divides the national government into the Legislative, Executive, and Judicial branches to ensure a separation of powers. This structure creates a system of checks and balances, where each branch has authority to check or restrain some of the powers of the other branches, requiring them to work cooperatively while safeguarding against the concentration of power.