Help me with this past past tense issue

[kaudes11114]

Q. Salt deposits and moisture threaten to destroy the Mohenjo-Daro excavation in
Pakistan, the site of an ancient civilization that flourished at the same time as the civilizations in the Nile Delta and the nver valleys of the Tigris and Euphrates

1.that flourished at the same time as the civilizations
2.that had flourished at the same time as had the civilizations
3.that flourished at the same time those had
4.flourishing at the same time as those did
5.flourishing at the same time as those were

hear 'the act of threatening' is in the past tense and 'the act of flourishing' is in past past tence ten also why answer 2 is wrong and 1 is correct.

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Hi kaudes11114,

In the original sentence, "Salt deposits and moisture threaten to destroy...." is a reference to something that is in the present tense (not the past tense). As the sentence continues, the "....ancient civilization that flourished at the same time as the civilizations...." refers to one time frame in the past and requires simple past tense (the verb "flourished" works perfectly).

IF the sentence made clear references to TWO past events, then the word "had" would be correct, but that didn't happen in this sentence.

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