Which enlightened thinker is most famous for his concept that the most effective form of government is one in which features separation of powers?

He is Baron de Montesquieu, which is a persuasive french author and keen to study of political rights, supposed britain was best ruled country of the time it was divided into 3 groups or officials which is the king executive, parliament legislative, judges in english courts judicial, called the division of power among different branches separation of powers. His idea as a part of on the spirit of laws and proposed separation of powers would keep any individual or group from gaining total control of government each branch would check the other and his ideas became the basis for united states constitution. The separation of powers based on the idea of Montesquieu in a government power must be in a division among different branches so one would not gain total control and each branch could check each other. 

It’s either d or b ! but it might be b