Atreaty signed by the president of the united states must be approved by two-thirds of the senate before it can go into effect. which principle of government does this reflect?

Your answer would be Checks and Balances.

Definition:

Checks and Balances:

A way to "counterbalance" the actions of organizations in the government, which would not give one branch all the power.

Explanation:

The reason why "checks and balances" would be the correct answer is because this is a way so that one of the branches in the government doesn't have more power over the other branches.

In your question, it says that the treaty that was signed by the President needs to be approved by 2/3 of the Senate, this would be known as checks and balances because it doesn't give the president all the power since the senate has to approve the treaty. It would not be fair if the president could sign a treaty and it will already go into affect, that would show that the President has more power over the senate. Also, if the president could sign a treaty and it will already go into affect, it would be bad because the President could make whatever treaty they want, and it will automatically pass if checks and balances didn't exist. Without checks and balances, there would be no use for having different branches in the government.