Answer: Communication and Distance barriers are being torn down by social media.
Step-by-step explanation:
In a passive voice scenario, the action is being done to the subject of the sentence instead of the subject being the one that is doing the action.
In the question, the subjects are "Communication and Distance barriers" and the action is "torn down".
In passive voice, the subjects need to be acted on by the action which is why "Communication and Distance barriers" are being torn down.