What stops one branch of government from becoming too powerful?

Why this is the answer

Either accepted answer names the same design. The Constitution splits the government's power into three branches so that no one person or group holds all of it, and that split creates a system of checks and balances: each branch can block, or threaten to block, what the others do. Two examples from the study materials make it concrete. The Senate, part of the legislative branch, can block a treaty the President signed. The Supreme Court, the judicial branch, can reject a law Congress passed. The point of the arrangement is to limit the government and keep it from violating people's rights. Memory hook: separation of powers divides the power, checks and balances let each branch stop the others.