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Sentence Correction: Comparatives - Superlatives

Historians are unsure whether the Black Death, one of the most devastating events in recorded human history, actually affected population levels or not since these levels had already begun a gradual decline due to living conditions years before.

Incorrect.

The original sentence uses or not after whether. Although this answer choice eliminates this original Redundancy error, it does so by using if instead of whether. In the GMAT, If is used in Conditionals only. If you see if in a sentence and there's no condition, you should replace if with whether.

Think of whether as a choice between two possibilities dealing with the same subject or as a yes/no question.

Example: I do not know whether this will work. (yes or no)

He was not sure whether he wanted banana or chocolate cake. (a choice between 2 possibilities)

Incorrect.

In the GMAT, the addition of the phrase or not at any point after the word whether is considered redundant.

Incorrect.

The original sentence uses or not after whether. Although this answer choice eliminates this original Redundancy error, it is grammatically incorrect. The superlative form, indicated here by the use of the word most, must be preceded by the word the. In this sentence, most devastating event in recorded human history is preceded by a.

Incorrect.

The original sentence uses or not after whether. Although this answer choice eliminates this original Redundancy error, it is stylisticially flawed. The unnecessarily wordy phrase which is known to be one of the most creates Redundancy.

Excellent job!

This answer choice eliminates the original redundancy mistake.

In the GMAT, the addition of the phrase or not at any point after the word whether is considered redundant.

Historians are unsure whether the Black Death, one of the most devastating events in recorded human history, actually affected population levels or not
Historians are unsure whether the Black Death, a most devastating event in recorded human history, actually affected population levels
Historians are unsure whether the Black Death, one of the most devastating events in recorded human history, actually affected population levels
The Black Death is one of the most devastating events in recorded human history, but historians are unsure if it actually affected population levels
Historians are unsure whether the Black Death, which is known to be one of the most devastating events in recorded human history, actually affected population levels