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Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.

(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.
Incorrect - It implies that many of the hills were dug - which is not logical

(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines.
Incorrect - It implies that many of the hills were dug - which is not logical

(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona.
Incorrect - the placement of modifier - ''most of them ... ago" is ambiguous. It can modify either the copper mines or the hills.

(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.
Correct - The sentence is clear, concise and with correct placement of modifier.

(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which are dug during the Greenwood copper boom a century ago.
incorrect - most of which were dug is the correct usage
Answer D
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B seems to be the best choice.
(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.
the pronoun"them" has no clear antecedent , the hills dug? doesn't make sense.

(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines.
"Dug..." modifies " the hills", and the second part of the sentence makes sense. "are" is correctly used to state a fact.

(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona.
" are dotting" - wrong tense. " most of them dug.." modifies " hundreds of copper mines"? doesn't work.

(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.
second part of the sentence is not independent. if it's a modifier, what does it modify - hills or mines? , and " them" has no clear antecedent.

(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which are dug during the Greenwood copper boom a century ago.
" Which" refers to " mines"? not clear. " are" is incorrect, past tense should be used.
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Answer is D
Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.

(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.
Dug should modify mines
(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines.
Same mistake as A
(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona.
unessential sentence construct distorts the intended meaning
(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.
Correct
(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which aredug during the Greenwood copper boom a century ago.
are is the wrong verb tense
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Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.

(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.
(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines.
(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona.
(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.
(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which aredug during the Greenwood copper boom a century ago.

The most suitable answer is (D) since it follows a topic position guideline, placing the topic that the sentence is going to be about near the start to prep the readers for what the paragraph will be about.
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the hills are dotted with mines that were dug a century ago.
Option D uses the correct construction to convey the meaning of the sentence.
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B as the opening modifier is clear.
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Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.

(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines. incorrect - unsuitable construction
(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines. - incorrect - many hundreds
(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona. incorrect - "are dotting"
(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago. correct
(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which are dug during the Greenwood copper boom a century ago. incorrect - present tense "are dug"
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Bunuel
Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.

(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.
(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines.
(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona.
(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.
(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which aredug during the Greenwood copper boom a century ago.


 


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(A) Many of them dug during the Greenwood copper boom a century ago should refer to the “mines”, not to “the hills”.
(B) Dug during the Greenwood copper boom a century ago, should refer to the “mines”, not to “the hills”.
(C) “are dotting# is the incorrect tense. The tense should be present simple.
(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.
Correct. The modifier is next to “mines” , and the verb is in present simple.
(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which are dug during the Greenwood copper boom a century ago. “are dug” should be “were dug” because it happened in the past.

However, I believe that the original sentence states “many of them”. That expression is changed for “most of them” in the other answers and thus, it changes the original meaning.
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Answer is : D
A) "Many of them dug during the Greenwood copper boom a century ago", should refer to the copper mines, but what follows is "the hills to the east"
B) "Dug during the Greenwood copper boom a century ago" should refer to the copper mines, but what follows and is modified is "the hills to the east"
C) This sentense is grammatically correct but the modifier (most of them dug during the Greenwood copper boom a century ago) seems to make the sentence elaborate.

D) This sentence is very precise/terse. The subject ( the hills to the east of death valley) and the verb ( dotted) are placed in the beginning of the sentence providing better clarity than C.

E) The mines were dug a century ago, so the phrase "which are dug" doesn't match the tense.
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(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines. - Wrong, Modifier/Pronoun Error - them is wrongly reflecting Hills or Mines

(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines. - Wrong, the Hills are not dug during the green wood copper boom

(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona - wrong - Verb tense error

(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago. - Correct

(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which aredug during the Greenwood copper boom a century ago- wrong - Verb tense error
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Bunuel
Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.

(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.
(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines.
(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona.
(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.
(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which aredug during the Greenwood copper boom a century ago.


 


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(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.INCORRECT
(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines.INCORRECT
(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona.INCORRECT
(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.INCORRECT
(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which aredug during the Greenwood copper boom a century ago.CORRECT

E
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Answer D

(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.

'Them' has no obvious referent; The sentence makes it sound as if the hills were dug during the boom as opposed to the copper mines.

(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines.

Makes it sound as if the hills were dug during the boom.

(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona.

'Are dotting' is a verb phrase that sounds as if the copper mines are actively dotting the hills as opposed to just existing all over the hills.

(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.

Correct!

(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which aredug during the Greenwood copper boom a century ago.

'Are dug' creates this weird present tense phrase even though the mines were dug a century ago.
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Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.

(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines. Incorrect as it says the hills were dug during copper boom

(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines. Incorrect as it says the hills were dug during copper boom

(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona. Copper mines dotting the hills is a plain fact so no use of present continuous tense so Incorrect

(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago. Correct

(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which are dug during the Greenwood copper boom a century ago. Incorrect as the mines were dug in past so using are is wrong.
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Option C,D,E are incorrect as copper mines are not dug but the hills are.

Option B is preferred over Option A as it is more precise

Posted from my mobile device
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Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.

(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.
(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines.
(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona.
(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.
(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which aredug during the Greenwood copper boom a century ago.
_______________________________________________
Explanation goes for
A- ''Many of them dug'' modifies ''hills''. Illogic meaning.
B - ''Dug during the ...'' modifies ''hills''. The same as in A.
C - Use of present continuous tense means that Mines are dotting the hills now. Intended meaning is not like that.
D- ''The hills ... are dotted with hundreds of copper mines'' - the sentence gives the intended meaning.
Moreover, ''most of them'' modifies ''mines''. Hold on that.
E - ''most of which are dug'' incorrectly uses present tense. Intended meaning of the sentence is about past.

D is our winner.
Hope, it helps.
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(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.
(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which are dug during the Greenwood copper boom a century ago.

Clearly D and E are the best expression of the intended meaning with the use of "the hills" as subject.
E out because "are" the action "be dug" already done a century ago => D

D
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(A) Many of them dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines.
The opening mod is wrongly modifying hills. Hills are not dug. It is the copper mines that ae dug

(B) Dug during the Greenwood copper boom a century ago, the hills to the east of Death Valley, Arizona, are dotted with many hundreds of copper mines.
The opening mod is wrongly modifying hills. Hills are not dug. It is the copper mines that ae dug


(C) Hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago, are dotting the hills to the east of Death Valley, Arizona.
Use of present continuous implies that copper mines are presently and actively dotting the hills which is a nonsensical meaning


(D) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of them dug during the Greenwood copper boom a century ago.
Tenses and modifier issues are resolved.


(E) The hills to the east of Death Valley, Arizona, are dotted with hundreds of copper mines, most of which aredug during the Greenwood copper boom a century ago.
Use of present tense 'are dug' is wrong here since the digging was done a century ago

Ans D
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