Sentence Correction

A site once used as an observatory by the Anasazi,ancient 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 ninteen-year cycle.

b)A recently discovered site was once used as 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 ninteen-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 ninteen- 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 ninteen-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 ninteen-year cycle at a recently discovered place that the Anasazi,ancient pueblo dwellers of new mexico,once used the site as an observatory.

[spoiler]OA is C. What is wrong with B?[/spoiler]

The usage of 'where' in B is not correct because it can either refer to the recently discovered site or New Mexico (which is closest to it).

Vemuri wrote:The usage of 'where' in B is not correct because it can either refer to the recently discovered site or New Mexico (which is closest to it).

Doesn't "where" incorrectly modify just New Mexico?

Can anyone tell what's wrong with D?

D and E are in passive voice...and a bit wordy too... so best avoided.
In Option B, block the prepositional phrase 'was once used as observatory by the Anasazi,ancient pueblo dwellers of New mexico,' the sentence will read : A recently discovered site...where patterns of light and shadow.

Similarly in C ,if you block the prepositional phrase 'once used as an observatory by the Anasazi,ancient pueblo dwellers of new mexico,' , the sentence will read: At a recently discovered site ..patterns of light and shadow were employed

C is clear as the verb 'at ' tells us what happened at a recently discovered site...