The correct answer is: "all of the above".
Any goverment (either at the federal, state or local level) has to be divided in three independent branches according to the principle of the division of powers: legislative branch (in the example: Congress at the federal level / state legislation at the state level / town council at the local level), executive power (President/ state governor / town supervisor) or judiciary level. Moreover, a system of checks and balances needs to be established to guarantee that none of the branches gathers enough power as to overrule the others.