Final answer:
In the U.S. government system, Congress can override a presidential veto and the judicial branch can rule congressional and executive actions unconstitutional. The executive branch cannot dissolve Congress, and the legislative branch cannot appoint Supreme Court justices on its own.
Step-by-step explanation:
The U.S. government system is characterized by checks and balances, a system designed to prevent any one branch from becoming too powerful. Of the statements you've listed, the ones that reflect actual checks in the U.S. government system are: 'Congress can override a presidential veto' and 'The judicial branch can rule congressional and executive actions unconstitutional'. These are key components of the checks and balances system.
However, 'The executive branch can dissolve Congress' is false as no branch has the power to dissolve another. Similarly, 'The legislative branch can appoint Supreme Court justices' is also false, it's the president (executive branch) who nominates justices, who are then confirmed by the Senate.
Learn more about Checks and Balances