Which statement best describes a sphere of influence?

Iran was independent, and Britain controlled trade in southern Iran

Explanation:

A Sphere of Influence is a region where some country or organization has some sort of exclusivity meant to serve the interests of powers outside the borders of the organization or country that controls it. The second and third options don't fit and seem to be more of a colonial situation. The first one doesn't really say anything. The fourth, though, clearly states that there was control over one area by an organization outside the borders.  Hope This Helps! Brainliest, Please?