A site once used as an observatory by the Anasazi, ancient pueblo

A site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, has been recently discovered where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

(A) A site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, has been recently discovered where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

(B) A recently discovered site was once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.
(C) At a recently discovered site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

(D) Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a site that was recently discovered and was once used by the Anasazi, ancient pueblo dwellers of New Mexico.

(E) Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a recently discovered place that the Anasazi, ancient pueblo dwellers of New Mexico, once used the site as an observatory.

The core theme of the passage is the discovery of ancient site. That it was used as a laboratory or some patterns were used to establish some things are incidental to the discovery as far as this topic is concerned. Hence, we must give the status of the verb to the discovery rather than for other things. Any modifier status such as the 'recently discovered' as in B, C,and E alter the original intent.
In D, the main verb is 'were employed rathr than has bben discocered"
A, by employing the verb 'has been discovered' for the subject of the site is the correct choice.

Official Explanation

Logical predication; Rhetorical construction

The most reasonable interpretation of this sentence is that there is a recently discovered site that was used as an observatory by the Anasazi, who were ancient pueblo dwellers of New Mexico. At this observatory, patterns of light and shadow were employed to establish the precise limits of the Sun and Moon over a nineteen-year cycle.

The correct answer choice will clearly convey this idea. However, the sentence as worded does not do so. There is no clear indication of when the patterns of light and shadow were employed for the indicated purpose.

A. This choice is incorrect for the reason indicated above.

B. This choice suggests that the entire clause where patterns of light and shadow were employed to establish the precise limits of the positions . . . actually modifies New Mexico rather than observatory.

C. Correct. This choice eliminates the above flaws; it clearly and cleanly conveys the intended idea.

D. This choice does not clearly convey the idea that the Anasazi used the site as an observatory, nor that they employed patterns of light and shadow for the purpose indicated.

E. This choice does not clearly convey the idea that the Anasazi employed patterns of light and shadow for the purpose indicated. Furthermore, at a recently discovered place that the Anasazi . . . once used the site as an observatory unnecessarily inserts the site, which is redundant (with place) and renders the sentence grammatically incorrect.

The correct answer is C.

VeritasKarishma mikemcgarry GMATNinja Hi could anyone please explain why the answer is C. Does'nt it say that at the recently discovered site they recently used patterns of shadow and light?

A site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, has been recently discovered where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

(A) A site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, has been recently discovered where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.- incorrect, the relative pronoun 'where' is too far from 'site' to which it should refer

(B) A recently discovered site was once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle. - incorrect, the relative pronoun 'where' is too far from 'site' to which it should refer

(C) At a recently discovered site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.- Correct

(D) Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a site that was recently discovered and was once used by the Anasazi, ancient pueblo dwellers of New Mexico.- incorrect, meaning change- Anasazi used the site as observatory is missing here

(E) Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a recently discovered place that the Anasazi, ancient pueblo dwellers of New Mexico, once used the site as an observatory.- incorrect, meaning change

AjiteshArun , GMATNinja , MagooshExpert , GMATGuruNY , VeritasPrepBrian , MartyTargetTestPrep , DmitryFarber , VeritasKarishma , generis , EducationAisle , other experts - please enlighten

1. Can we use the reason stated in option a and b to eliminate them?
2. Can you please provide a POE for this question?

The meaning is quite clear in option (C).

(C) At a recently discovered site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

We have a recently discovered a site. It was once used as an observatory by the Anasazi. At this site, patterns of light and shadows were employed to establish something for 19 years. (Since patterns were employed for 19 years, they cannot be employed recently)

(C) At a recently discovered site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.


I think the intended meaning is that- Anasazi used the site as an observatory and they employed patterns of light and shadow.

To me the sentence at C sounds ambiguous. patterns of light and shadow were employed by Angazi is missing for me.

At a recently discovered site once used as an observatory by the Anasazi, patterns of light and shadow were employed by the government/ by the US Army/ by Mr, Trump?

AjiteshArun , VeritasKarishma generis - What am I missing here? Where am I wrong?

So the original sentence - There is a site that was used as an observatory by the Anasazi once upon a time.
2) The Anasazi were ancient pueblo dwellers of New Mexico.
3) This site was recently discovered, at this site patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.


Now going to the options


(A) A site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, has been recently discovered where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle. *where does not modify site, it is too far.

(B) A recently discovered site was once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle. *Where incorrectly modifies New Mexico*


(C) At a recently discovered site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle. CORRECT

(D) Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a site that was recently discovered and was once used by the Anasazi, ancient pueblo dwellers of New Mexico. * Meaning change* Also, I like to see sentence written in active voice.

(E) Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a recently discovered place that the Anasazi, ancient pueblo dwellers of New Mexico, once used the site as an observatory. *Misplaced Modifier*
Again, I like to see sentence written in active voice.

I don't see a problem with (C)

I employed patterns of light and shadow to establish the precise limits of the positions of the Sun and Moon.

employ can mean 'to use' too, not just 'to hire'.

Hi Akash, that is correct.

I suppose this interpretation cannot be entirely ruled out. However, if the intended meaning indeed was that Anasazi used this site earlier and now, the US Army is using it, then a past perfect would perhaps have been a better usage:

Patterns of light and shadow were employed by the US Army at a recently discovered site that had once been used as an observatory by the Anasazi.

Hello Everyone!

Let's tackle this question, one thing at a time, and narrow down our options quickly so we know how to answer questions like this when they pop up on the GMAT! To begin, let's take a quick look at the question and highlight any major differences between the options in orange:

A site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, has been recently discovered where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

(A) A site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, has been recently discovered where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

(B) A recently discovered site was once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

(C) At a recently discovered site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

(D) Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a site that was recently discovered and was once used by the Anasazi, ancient pueblo dwellers of New Mexico.

(E) Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a recently discovered place that the Anasazi, ancient pueblo dwellers of New Mexico, once used the site as an observatory.

After a quick glance over the options, we can see that each one is organized differently than the rest. Whenever you see an entire sentence underlined on the GMAT, it's a clue that you should be looking at bigger issues, such as modifiers, organization, and meaning.

Since the modifier "ancient pueblo dwellers of New Mexico" is located directly next to its antecedent "Anasazi," we can skip focusing on that modifier. It was an easy one meant to distract you anyway! Instead, let's look at the overall organization of each sentence and see if we can find problems with meaning, other modifiers, and organization:

(A) A site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, has been recently discovered where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

This is INCORRECT because the modifier "where patterns of light and shadow were employed" is not located anywhere near its antecedent "site." The closest thing to it that it might be referring back to is New Mexico, which would be wrong.

(B) A recently discovered site was once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

This is also INCORRECT because the modifier "where patterns of light and shadow were employed" is located right after New Mexico, which is NOT what it should be modifying - it should be closer to "site."

(C) At a recently discovered site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

This is CORRECT! There is no modifier problem here because the writer took out the word "where," changing the phrase from a modifier to a clause. If you took out the modifier "ancient pueblo dwellers of New Mexico," the sentence would stand as it is just fine!

(D) Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a site that was recently discovered and was once used by the Anasazi, ancient pueblo dwellers of New Mexico.

This is INCORRECT because it changes the meaning of the original sentence! The phrase highlighted in red says that some other entity or group employed patterns of light and shadow, not the Anasazi. This isn't the meaning we're going for. It's also not ideal on the GMAT to use passive voice ("was recently discovered" / "was once used") whenever possible.

(E) Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a recently discovered place that the Anasazi, ancient pueblo dwellers of New Mexico, once used the site as an observatory.

This is INCORRECT for the same reason as option D - the meaning is changed from the Anasazi employing patterns of light and shadow to some "other" person or group doing it. Also, if you read the sentence without the modifier "ancient pueblo dwellers of New Mexico," it doesn't sound great, either:

Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a recently discovered place that the Anasazi once used the site as an observatory.

There you have it - option C is our choice! It's the only one that uses modifiers correctly without changing the overall meaning.


Don't study for the GMAT. Train for it.

A site has been recently discovered. The site was once used by the Anasazi as an observatory. At this site, patterns of light and shadow were employed to establish the limits of the positions of the Sun and Moon over a time period.

The relative clause (“where” clause) appears after the verb and is thus incorrectly placed. It needs to appear right after the noun it modifies.


A. A site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, has been recently discovered where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.
Incorrect. For the reason stated above.

B. A recently discovered site was once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, where patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

Incorrect. Here, “where” seems to refer to Anasazi.

C. At a recently discovered site once used as an observatory by the Anasazi, ancient pueblo dwellers of New Mexico, patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle.

Correct. The structure of this option is as follows:


D. Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a site that was recently discovered and was once used by the Anasazi, ancient pueblo dwellers of New Mexico.

Incorrect. For the following reasons:

1. This option doesn’t mention that the site was used as an observatory by the Anasazi
2. The positioning of the prepositional phrase “at a site” creates confusion as to what it modifies. Given the placement, it can modify cycle, positions, or “were employed”.

E. Patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle at a recently discovered place that the Anasazi, ancient pueblo dwellers of New Mexico, once used the site as an observatory.
Incorrect. For the following reasons:

1. The use “the site” is incorrect since “that” already refers to the place. Without “the site”, the “that” clause will be fine.
2. The positioning of the prepositional phrase “at a recently discovered place” creates confusion as to what it modifies. Given the placement, it can modify cycle, positions, or “were employed”.

GMATNinja, could you please please help us with this question? There's a lot of confusion on what is the intended meaning of the sentence.

Please!

Thank you.

VeritasKarishma GMATNinja

I have a query regarding ambiguity with option C. I agree that we have reasons to eliminate all other options and only option C is left over, but doesn't the clause patterns of light and shadow were employed to establish the precise limits of the positions of the Sun and Moon over a nineteen-year cycle. convey ambiguous meaning as to when the patterns were used ? Were they used by Anasazi in the past or used by someone after the the site was discovered recently. Can you please clarify ? Or am I thinking too much and is irrelevant in context of the question ?

From the details given in the sentence it is clear that the patterns were employed when it was used as an observatory.
It tells us that the site was discovered recently.
It also tells us that patterns were employed to establish positions over a 19 year cycle. Then this must be when the site was being used as an observatory.

hello AndrewN,

I was wondering whether you could provide us your opinion over this one,

Regarding answer choices A,B would you consider the placement of ", ancient pueblo dwellers of New Mexico" erroneous? Specifically, I think that , ancient pueblo dwellers of New Mexico , modifies "the Anasazi" , but is there a risk that it might actually modify the subject of the clause which is "the site" ?
I eliminated A,B because of the placement of "where" .

Hello, UNSTOPPABLE12. I traced the same line of reasoning to eliminate (A) and (B). Specifically, I was a little hesitant about the appositive phrase ("ancient pueblo dwellers..."), but it was not until I hit where that I had had enough and sought a better alternative. I wanted where to be in which instead. (C) through (E) discard the word altogether, allowing us to focus more on meaning, and the latter two options adopt a passive construct that skews the timeline: we do not see mention of the Anasazi until late in the sentence, so everything up to that point has sort of been floating around in our head, waiting for a logical anchor point. Certainly that is not the best way to express that the Anasazi, at a basic level, did something.

- Andrew

Hello, GMATNinja

In option B,


Granted, where incorrectly modifies New Mexico.
But the red part does not look like a modifier, as you mentioned in your solution, but a sentence in itself (was once used). Then, why does it have the same error as A?

Also, I am STILL having trouble grasping the intended meaning. If the site was 'recently' discovered, how could patterns be employed at the site over a '19-year' time period? Shouldn't the meaning suggest that the patterns were employed when the site was used (back in the day) as an observatory by the Anasazi?

Please clarify this meaning. I've got it wrong the second time.