The correct answer is option B: The State's Constitution.
The reason why a State's Constitution is in charge of establishing all three branches of any particular State's Government is because all States are modeled directly on the Federal Government. The Federal Government's 3 branches of power are set by the US Constitution.
According to the US Constitution, the Legislative Branch duty is to write or make the Laws. The Judicial Branch's duty is to interpret the laws and the Executive branch to execute the law. Therefore, if State are modeled on the Federal Government, it follows that the State's Constitution would be in charge of establishing the three branches of State government.
