Since Marbury v. Madison, the judicial branch has determined whether decisions of other governmental entities are?

The correct choice emphasizes that since the landmark case of Marbury v. Madison in 1803, the primary role of the judicial branch is to interpret the Constitution and assess whether the actions of other governmental entities are constitutional. This case established the principle of judicial review, which allows the judiciary to invalidate laws and executive actions that they find to violate the Constitution.

The significance of Marbury v. Madison cannot be understated, as it confirmed the judiciary's role as a check on the legislative and executive branches, ensuring that all government actions align with constitutional mandates. This foundational principle is essential to maintaining the rule of law and protecting individual rights as enshrined in the Constitution.

Other choices do not address the core function established by Marbury v. Madison. For instance, being able to propose amendments pertains instead to the legislative process, while the notion of supporting each other does not accurately reflect the legal authority or purpose of the judicial branch per the rulings that stemmed from this historic case. Therefore, the emphasis remains squarely on the ability of the judiciary to interpret and uphold constitutional law.