The correct sentence is (A). In this example the author stablishes a good parallel structure when he/she enumerates the items. Commas must not be used in an independent clause; in particular, before a verb (the comma before “were” is not correct as an example B).
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Answer: umm look on google
Explanation: and copy paste your question
Answer: I believe it would be letter (b)
Explanation: I had to answer this question yesterday and I am pretty sure this is the answer. Because it asks ¨the narrator gives an example of why oxygen is vital to climbers on Mt. Everest. How does the narrator develop this concept in the rest of the narrative?¨ so this is really the only plausible answer regarding the question.
