D) is the right answer.

a,c - "Requires that" is incorrect
b,e - "it" has no antecedant.

Answer is D

The U.S. National Park Service's mission requires that they promote and regulate the use of the national parks and that they preserve the character and natural and historical value of the parks.

A. that they promote and regulate the use of the national parks and that they preserve - Incorrect - 'they' here refers to U.S. National Park Service's mission, which does not make sense

B. it to promote and regulate the use of the national parks and must also work to preserve -Incorrect - 'it' here refers to U.S. National Park Service's mission, which does not make sense


C. that they promote and regulate the use of the national parks and they preserve - Incorrect - 'they' here refers to U.S. National Park Service's mission, which does not make sense


D. the promotion and regulation of the use of the national parks and the preservation of - Correct - the mission requires the promotion and regulation of (...) and the preservation of (..) - parallel and makes sense

E. it to promote and to regulate the use of the national parks and the preserving of - Incorrect - 'it' here refers to U.S. National Park Service's mission, which does not make sense

Hi,
As only possessive pronouns can refer back to possessive subjects, usages of 'it' and they to refer back to U.S.National Park Service is incorrect.
Moreover there are other errors as well
No reference to plural pronoun 'they' in A and C
requires is there so must is redundant in B
promote, regulate and preserving are not parallel in E

promotion, regulation, preservation are all parallel in D

Hence, D

The U.S. National Park Service's mission requires that they promote and regulate the use of the national parks and that they preserve the character and natural and historical value of the parks.

A. that they promote and regulate the use of the national parks and that they preserve

Requires that they is incorrect usage

B. it to promote and regulate the use of the national parks and must also work to preserve

Not clear what it refers to in this one

C. that they promote and regulate the use of the national parks and they preserve

Requires that they is incorrect usage

D. the promotion and regulation of the use of the national parks and the preservation of

This has correct usage in terms of requires the and the meaning comes out most clearly in this

E. it to promote and to regulate the use of the national parks and the preserving of

Not clear what it refers to in this one

Correct answer is D

"they" can't be used for singular noun. hence A and C are out.

in B "to promote and regulate" is not parallel with "must also work to preserve"

in E "to promote and to regulate" are not parallel with "the preserving of"

D is perfect as it shows the correct parallelism between "the promotion and regulation of" and "the preservation of"



CORRECT Answer is D

I will go with C.

Option D mentions about promotion, regulation and preservation.

However original meaning is that mission should promote,regulate and preserve. This is captured in C.

Cheers

Atul

Moreover in (A) and (C) "The U.S. National Park Service's mission" cannot be referred as "They" and similarly "It" cannot be used in place of "The U.S. National Park Service's mission" as The U.S. National Park Service's mission is a possessive subject and can only be refereed back as possessive pronouns.

The answer in my opinion is D

A. 'THEY' refers to the National PArk Service's mission, which is incorrect.
B.Even in this case, 'IT' is incorrectly used to address U.S National Park Service's mission.
C.Again, 'THEY' is incorrectly used.
E.Again, 'IT' is incorrectly used and there is no parallelism in the sentence.

D. Perfect choice from the options.Confirms to parallelism and Subject - Verb Agreement.

The U.S. National Park Service's mission requires that they promote and regulate the use of the national parks and that they preserve the character and natural and historical value of the parks.

A. that they promote and regulate the use of the national parks and that they preserve

Incorrect: They has no precedence

B. it to promote and regulate the use of the national parks and must also work to preserve
Incorrect: "it" is incorrect; must also is redundant.

C. that they promote and regulate the use of the national parks and they preserve
Incorrect: They has no precedence

D. the promotion and regulation of the use of the national parks and the preservation of

Correct: good parallelism;conveys the meaning concisely

E. it to promote and to regulate the use of the national parks and the preserving of

Incorrect: after "and" , the preserving is not parallel to previous part;furthermore, the preserving should not be used when we have "the promotion" already.