Without hiding the fact that the destruction of Athens was one of their most important objectives, the multitudinous Persian army, led by Xerxes and nine of his generals, marched westward toward Greece in the spring and summer of 480 BCE.

A. was one of their most important objectives
B. was one of its most important objectives
C. was one of the objectives they considered to be most important
D. having been one of its most important objectives
E. is one of its most important objectives
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Without hiding the fact that the destruction of Athens was one of their most important objectives, the multitudinous Persian army, led by Xerxes and nine of his generals, marched westward toward Greece in the spring and summer of 480 BCE.

A. was one of their most important objectives - Its because the pronoun refers to army which is collective noun. Hence singular.
B. was one of its most important objectives - Hold. Seems correct.
C. was one of the objectives they considered to be most important - Same as A
D. having been one of its most important objectives
E. is one of its most important objectives - Tense is past> "was" instead of is
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B is the correct answer

past tense should be used as it happened in the past "was" and the pronoun should refere to the army "it's"

B& C left; C is too wordy and B is the correct answer
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KAPLAN OFFICIAL EXPLANATION:

B.

The issue here is the pronoun their. Usually a pronoun comes after its antecedent, but here the pronoun precedes what it refers to—the singular Persian army, not the plural Xerxes and 9 of his generals. The answer, then, will use the singular its instead of their. So (A) and (C) are out.

(D) uses its, though it incorrectly changes the verb was to the participle having been (thus creating a clause without a verb). (E) changes the verb was to is, and destroys the correct sequence of tenses based on marched. (B) is correct.
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