D.
(Enslaved many Native Americans) is the answer I'm pretty sure.
The thinker that introduced the idea of a separation of powers for effective government is a French political philosopher Montesquieu in De l’esprit des lois.
<h3>What is the idea of separation of power?</h3>
Separation of power means separation of government into three forms, judicial, legislative, and executive.
The system was introduced to lower the arbitrary of the government, because if any law is passed it has to be accepted by three government.
Thus, the thinkers is a French political philosopher Montesquieu in De l’esprit des lois.
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