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 ends with a noun, pronoun, gerund, or clause. 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. The other sentences do not have clear prepositional phrases.

Answer:

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