CR: In the vast majority of cases, when people are stopped

[direstraits007]

In the vast majority of cases, when people are stopped by airport security clearance, it is because they are carrying small bits of metal, such as coins, that cannot be used as weapons, but are large enough to be picked up by highly sensitive metal detectors. Since virtually everyone carries such pieces of metal, and the weapons that are smuggled onto planes are often not made of metal, highly sensitive metal detectors have outlived their usefulness. Lowering the sensitivity of these metal detectors so that they only detect large pieces of metal would reduce the frequency with which innocent passengers are stopped without hampering security’s ability to screen for weapons.

Which of the following, if true, is most useful to support the claim that this proposal would have its desired effect if it were carried out?

(A) Airport metal detectors, when set to higher levels of sensitivity, will not react to wristwatches, belt buckles, or the small rivets commonly used on travelers’ jeans.

(B) The maintenance and electricity costs associated with metal detectors are far lower when detectors are utilized at a high level of sensitivity than when they are used at a lower level of sensitivity.

(C) A metal detector with a low level of sensitivity can provide more information about what type of weapon a person is carrying, if they are carrying a weapon, than can a metal detector with a high level of sensitivity.

(D) In some cases, passengers who are stopped because they are only carrying coins are found to be smuggling non-metal weapons.

(E) Some weapons that are not made primarily out of metal include small bits of metal used as fasteners or serial number plates.

OA: A
source: Knewton GMAT

I would opt for C. Can anyone tell how can A be the answer?

Thanks!

GeeMate.

[carole.okigbo]

OA is C

http://gmatclub.com/forum/this-cr-reall ... 89384.html

[RonPurewal]

In the vast majority of cases, when people are stopped by airport security clearance, it is because they are carrying small bits of metal, such as coins, that cannot be used as weapons, but are large enough to be picked up by highly sensitive metal detectors. Since virtually everyone carries such pieces of metal, and the weapons that are smuggled onto planes are often not made of metal, highly sensitive metal detectors have outlived their usefulness. Lowering the sensitivity of these metal detectors so that they only detect large pieces of metal would reduce the frequency with which innocent passengers are stopped without hampering security’s ability to screen for weapons.

Which of the following, if true, is most useful to support the claim that this proposal would have its desired effect if it were carried out?

(A) Airport metal detectors, when set to higher levels of sensitivity, will not react to wristwatches, belt buckles, or the small rivets commonly used on travelers’ jeans.

(B) The maintenance and electricity costs associated with metal detectors are far lower when detectors are utilized at a high level of sensitivity than when they are used at a lower level of sensitivity.

(C) A metal detector with a low level of sensitivity can provide more information about what type of weapon a person is carrying, if they are carrying a weapon, than can a metal detector with a high level of sensitivity.

(D) In some cases, passengers who are stopped because they are only carrying coins are found to be smuggling non-metal weapons.

(E) Some weapons that are not made primarily out of metal include small bits of metal used as fasteners or serial number plates.

OA: A
source: Knewton GMAT

I would opt for C. Can anyone tell how can A be the answer?

Thanks!

GeeMate.

this is a weird question -- answer choice (c) is logically correct, but it just doesn't make a lot of sense.

specifically, the "desired effect" of the proposal is to decrease the hassle for innocent passengers by lowering the sensitivity of the detectors, while still retaining the ability to screen for weapons.

choice (c) actually says that metal detectors with lower sensitivity will actually be better at detecting weapons!
if this statement is taken to be true, then, of course, it's perfect for the purposes of this passage: it actually shows that lowering the sensitivity of the detector will not only benefit innocent passengers, but will actually improve the airport's ability to detect weapons.

if this question is difficult, then, the main reason is that this choice just doesn't make any sense from a common-sense standpoint: it's absurd that a metal detector with lower sensitivity would somehow be able to pick up finer details than would a metal detector with higher sensitivity. (this actually seems to go against the very definition of the word "sensitivity".)

still, from a perfectly formal logical standpoint, it's pretty clear that (c) is the answer.