Alamos National Laboratory

[Capthan]

Pioneered by scientists at Los Alamos National Laboratory,BEAM roborts are not programmed to walk; instead they use brainlike circuts called neural networks to learn to walk through trial and error.

A. BEAM robots are not programmed to walk; instead they use brainlike circuits called neural networks to learn to walk through trial and error
B. BEAM robots learn to walk through trial and error by using brainlike circuits called neural networks instead of by programming them
C. BEAM robots are not being programmed to walk but instead using brainlike circuits called neural networks and learning to walk through trial and error
D. brainlike circuits called neural networks are used instead of programming for BEAM robots learning to walk through trial and error
E. brainlike circuits called neural networks are being used for BEAM robots that learn to walk through trial and error instead of being programmed

Please explain why it is not B.

[gmattaker]

Is it "A"

[RonPurewal]

in choice (b), 'by programming them' doesn't make sense.

to see why, drop the modifier ("called neural networks"), which doesn't affect the sentence's grammar or parallelism, and observe the result:
Pioneered by scientists at Los Alamos National Laboratory, BEAM robots learn to walk through trial and error by using brainlike circuits instead of by programming them

there are two things very, very wrong here with this illogical parallelism (notice that the parallelism is 100% ok from a purely [i]grammatical standpoint; it's only incorrect because it makes no logical sense).
first, the faulty parallelism implies that the robots themselves are programming things, because "by programming..." is grammatically, and therefore logically, parallel to "by using..." (which refers to the robots).
second, according to the parallelism, "them" would refer to the circuits, not the robots. in fact, "them" can't refer to the robots in this construction, because "robots" is actually still the subject at this point. if "them" were to refer to the robots, it'd have to appear as "themselves" - which would be grammatically ok, but still absurd.

so overall, choice (b) says that robots are programming circuits, when it's supposed to say that humans are programming robots.
not good.

the correct answer is (a).

[Guest]

I eliminated A because "they" has no clear referrent. First, it is used after a semi-colon. Second, it could refer to "scientists" or "robots". What am I doing wrong?

[RonPurewal]

I eliminated A because "they" has no clear referrent. First, it is used after a semi-colon. Second, it could refer to "scientists" or "robots". What am I doing wrong?

there's nothing wrong with using a pronoun after a semicolon.

i see your point about the pronoun reference.
if anything, we're learning something new here about the gmat's use of pronouns; apparently, they'll tolerate a bit of pronoun ambiguity, as long as the pronoun is grammatically parallel to the intended referent, AND EXTREMELY nonparallel to the possible "second referent".

here's another case in which the same thing happens:
http://www.manhattangmat.com/forums/post5232.html
http://www.manhattangmat.com/forums/pro ... t2809.html

clearly, pronoun ambiguity has a lower priority level, as an error, than do more blatant grammatical problems - especially when the intended referent is clearly parallel to the pronoun.

[jackabigail]

in choice (b), 'by programming them' doesn't make sense.

to see why, drop the modifier ("called neural networks"), which doesn't affect the sentence's grammar or parallelism, and observe the result:
Pioneered by scientists at Los Alamos National Laboratory, BEAM robots learn to walk through trial and error by using brainlike circuits instead of by programming them

there are two things very, very wrong here with this illogical parallelism (notice that the parallelism is 100% ok from a purely [i]grammatical standpoint; it's only incorrect because it makes no logical sense).
first, the faulty parallelism implies that the robots themselves are programming things, because "by programming..." is grammatically, and therefore logically, parallel to "by using..." (which refers to the robots).
second, according to the parallelism, "them" would refer to the circuits, not the robots. in fact, "them" can't refer to the robots in this construction, because "robots" is actually still the subject at this point. if "them" were to refer to the robots, it'd have to appear as "themselves" - which would be grammatically ok, but still absurd.

so overall, choice (b) says that robots are programming circuits, when it's supposed to say that humans are programming robots.
not good.

the correct answer is (a).

Dear Ron

It is my honor to ask you a question regarding this problem. Why D and E are wrong? Some people say modifer false, I do not understand, can the brainlike circuits modified by pioneered? I think it is fine. CAn you help me with this? The tesst date is approaching, really need your help. Thanks a lot

[mschwrtz]

When a sentence begins with a participial phrase followed by a comma, the participial phrase will either modify the subject of the main clause or attribute action to the subject of the main clause, which subject will immediately follow the comma.

In this sentence, the participial phrase Pioneered by scientists at Los Alamos National Laboratory should modify BEAM robots, so BEAM robots must follow the comma.

[iatbitw7]

[code][/code]
could anyone tell me what's wrong with C

[jnelson0612]

[code][/code]
could anyone tell me what's wrong with C

Sure!

BEAM robots are not being programmed to walk but instead using brainlike circuits called neural networks and learning to walk through trial and error

1) "not being programmed" is a different meaning from "not programmed". "being" implies that something is currently happening.

2) verbs: They are "not being programmed" to walk but instead "USE" circuits called neural networks and "LEARN" to walk.

For example:
I do not cheat but instead USE my brain to think of the answers. is correct
NOT
I do not cheat but instead USING my brain to think of the answers.

[aakash.saxena33]

whats wrong with D ?

[aakash.saxena33]

A clause after semi colon must be an independent sentence which is not the case in "A". in A, they refers to nothing.

[tim]

A clause after semi colon must be an independent sentence which is not the case in "A". in A, they refers to nothing.

did you not read the part where Ron said the answer was A *and* where he explained this point exactly? we definitely have independent clauses on both sides of the semicolon; you may want to review the definition of independent clauses. because the two sides are technically part of the same sentence, "they" can most definitely refer back to an antecedent in the first half..

[tim]

whats wrong with D ?

Michael already explained this. Please read the entire thread before asking a question that has already been asked and answered..

[cgrcrs02]

With D and E, why can't "brainlike circuits called neural networks" be the subject? I understand D and E would still be wrong for parallelism, but not for subject reference. Please advise

Thanks,
Srini

[jlucero]

With D and E, why can't "brainlike circuits called neural networks" be the subject? I understand D and E would still be wrong for parallelism, but not for subject reference. Please advise

Thanks,
Srini

Those could be a subject of a sentence, but then the opening modifier is modifying circuits instead of BEAM robots. Also, the main idea of the sentence changes from what BEAM robots can do, to circuits are being used. Each of these are reasons to eliminate D/E.