Choice "D" is correct. Since the a primary purpose of the firewall is to prevent unauthorized access to the network, requiring all users to have a password helps to minimize vulnerability.
Choice "a" is incorrect. Collusion would not be minimized at all by requiring employees to have passwords; the employees conspiring to do bad things could merely share their passwords.
Choice "c" is incorrect. Passwords would not do anything about data entry errors.
Choice "b" is incorrect. The usage of passwords or the lack of passwords would have no effect on failure of the server duplicating function.
