The most appropriate formal style revision from the given options is: If people are unable to look away from their smart phones and communicate with the world, then it will be in the end of civilization.
The correct answer is option A.
Option A maintains a formal tone by using the term "people" instead of the more casual "individuals" and avoids unnecessary specifics or predictions about the quality of interpersonal communication. It communicates the core idea with clarity and conciseness, adhering to a formal style.
The original sentence suggests a dire consequence for societal behavior related to smartphone usage. By framing it as a conditional statement without introducing additional conditions or predictions, option A maintains a straightforward and formal presentation of the argument.