A new electronic security system will only allow a single pe

[BTGmoderatorAT]

A new electronic security system will only allow a single person at a time to pass through a secure door. A computer decides whether or not to unlock a secure door on the basis of visual clues, which it uses to identify people with proper clearance. The shape of the head, the shape and color of the eyes, the shape and color of the lips, and other characteristics of a person's head and face are analyzed to determine his or her identity. Only if the person trying to open a secure door has the required clearance will the door unlock. Because this new system never fails, an unauthorized person can never enter a secure door equipped with the system. If the statements above are true, which of the following conclusions can be most properly drawn?

(A) The new system is sure to be enormously successful and revolutionize the entire security industry.
(B) The new system can differentiate between people who are seeking to open a secure door and people passing by a secure door.
(C) No two people have any facial features that are identical, for example, identical lips.
(D) High costs will not make the new security system economically unviable.
(E) The new computer system is able to identify some slight facial differences between people who look very similar, such as identical twins.

I'm confused between B & E. Can any experts help?

[DavidG@VeritasPrep]

A new electronic security system will only allow a single person at a time to pass through a secure door. A computer decides whether or not to unlock a secure door on the basis of visual clues, which it uses to identify people with proper clearance. The shape of the head, the shape and color of the eyes, the shape and color of the lips, and other characteristics of a person's head and face are analyzed to determine his or her identity. Only if the person trying to open a secure door has the required clearance will the door unlock. Because this new system never fails, an unauthorized person can never enter a secure door equipped with the system. If the statements above are true, which of the following conclusions can be most properly drawn?

(A) The new system is sure to be enormously successful and revolutionize the entire security industry.
(B) The new system can differentiate between people who are seeking to open a secure door and people passing by a secure door.
(C) No two people have any facial features that are identical, for example, identical lips.
(D) High costs will not make the new security system economically unviable.
(E) The new computer system is able to identify some slight facial differences between people who look very similar, such as identical twins.

I'm confused between B & E. Can any experts help?

We know that the security system decides whether to open the door on the basis of visual clues. And we know that it never fails - meaning it only allows those with clearance to unlock the doors. Based on that, would B have to be true? Not necessarily. If an unauthorized person is simply walking by, the door won't open, and if an unauthorized person is attempting to open the door, the door won't open. Either way, the system doesn't fail, and so it's irrelevant whether the system can tell the difference between the two scenarios.

E, on the other hand, has to be true. If the system couldn't differentiate between similar looking people, then if one person with clearance had an identical twin who did not have authorization, that unauthorized twin would be able to open the door, thus violating the premise that the system never fails. So if the system never fails, we can conclude that it must be able to differentiate between similar-looking people.