Sentence Correction (SC) | Re: OG 2018 New: Air traffic routes over the North Pole

though the sentence is underlined, the same method is applied. first, try to realize grammatical roles of each phrase when you read. immediately, when you see any grammatical role not logic, you find an error. good knowledge of grammar patterns and a sense of logic is required.

apply above rule

read choice a. at first , we see "it" is not clear. "it is found to be" is good pattern if "it" is real subject, not fake subject. for example,
the cup is good. it is found
...

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