Iran remained a politically independent nation. however, russia controlled trade in northern iran, and britain controlled trade in southern iran. this is an example of a.
colony
protectorate
sphere of influence

The correct answer is Sphere of influence

Explanation:

The concept sphere of influence refers to an exclusive power a country has over the economy, military forces or politics of a different country and that mainly benefits the country the outsider nation. This concept differs from the colony and from protectorate because in the sphere of influence only certain aspects of the country being influenced are controlled and the territory does not belong to the nation that is influencing it. This commonly occurs with powerful nations with interests, this was the case of Iran that was controlled by both Britan and Russia between the 19th and the 20th century in terms of economics, without becoming a colony of the empires as Iran was politically independent. Therefore, in the case of Iran that remained politically independent but was controlled by Russia and Britain, this is an example of "Sphere of influence".

july 1861 here you go hope it

bibliography and citations to credit the sources hope this you if not my deepest of apologize ^w^