Question

which sentence uses a prepositional phrase?
given the economic and political unrest, the family decided to emigrate
ruling brutally, the harsh dictator caused many people to flee the country
increasing tensions required that international diplomats begin to negotiate
some editorials exposing government corruption were leaked to the public

Explanation:

A prepositional phrase starts with a preposition and includes its object. In "Given the economic and political unrest, the family decided to emigrate", "Given the economic and political unrest" is a prepositional - like phrase functioning as an adverbial phrase indicating the reason. In other sentences, there are no such clear - cut prepositional phrases.

Answer:

Given the economic and political unrest, the family decided to emigrate