Why Did Jews Establish Eruvin More Than 2,000 Years Ago

Why did Jews establish eruvin more than 2,000 years ago?

A) To form a their own governmental unit
B) To form a common-interest association based on bureaucracy
C) To allow them to adhere to their religious laws
D) To allow them to live separated from the entrance of any outsiders
E) To form a communal identity that had no involvement with the surrounding society