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Sentence Correction: Dangling Modifiers - Overview

Reading reports and comparing statistical analyses, authorities gather information about the weather along a flight route, but in some cases they find it particularly difficult to decide whether to approve a flight or not.

Although this answer choice corrects the redundancy in the original sentence by removing the phrase or not, it creates a Dangling Modifier. The original sentence begins with a modifier: Reading reports and comparing statistical analyses. A modifier should be placed right next to the noun it describes. The only noun that this modifier can logically modify is authorities. However, what immediately follows the modifier is information and information cannot read.

What helps us identify this question as a Dangling Modifier question as well as identify the mistake is the following Stop Sign:

A modifier, characterized by all of the following:
1. Verb+ing or Verb in 3rd form
2. Separated from the rest of the sentence by a comma
3. Appears at the very beginning of the sentence

Whenever you see this Stop Sign, focus on the modifier: check whether the noun right after the modifier is indeed the noun that the modifier describes. If it isn't - you've found your mistake.

In the GMAT, the addition of the phrase or not at any point after the word whether is considered redundant and, therefore, a stylistic error. Look for a more concise answer choice.

This answer choice repeats the original Stylistic error. In the GMAT, the addition of the phrase or not at any point after the word whether is considered redundant. Look for a more concise answer choice.

Although this answer choice corrects the redundancy in the original sentence by removing the phrase or not, in the GMAT, the word if should be used in Conditionals only. Since in this question there is no condition, if should be replaced by whether.

Whether is used 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)

Nice work!

In the GMAT, the addition of the phrase or not at any point after the word whether is considered redundant and, therefore, a stylistic error.

authorities gather information about the weather along a flight route, but in some cases they find it particularly difficult to decide whether to approve a flight or not
authorities gather information about the weather along a flight route, but in some cases they find it particularly difficult to decide if a flight should be approved
information about the weather along a flight route is gathered by authorities, but in some cases they find it particularly difficult to decide whether to approve a flight
authorities gather information about the weather along a flight route, but in some cases they find it particularly difficult to decide whether to approve a flight
authorities gather information about the weather along a flight route, but in some cases they find it particularly difficult to decide whether or not to approve a flight