What checks and balances exist between the branches of government?

To start, checks and balances in between the branches is the process of all three branches checking one another so that the branches remain balanced and not corrupt.

Examples of checks and balances in the government might be if the legislative branch were to make a law, this law would first have to go to the executive branch to have the president approve. If the president finds this law unconstitutional or corrupting, he/she has the right to veto or reject this law.

Another example would be when the Judicial branch checks a law made and accepted by the legislative branch. The Judicial branch will decide whether this new law is constitutional.

to act quickly in times of danger to the united states

because you have to act quickly if you want to live/survive.