Answer:
1.a system that allows each branch of a government to amend or veto acts of another branch so as to prevent any one branch from exerting too much power.
Definition of in someone's power
1: in a position of being controlled by someone other than oneself
She had them in her power.
2: able to be done by someone: within one's ability
It's in your power to change the way things are done here.
I'll do everything in my power to help.
Explanation: