GMAT Sentence Correction (SC) | To Josephine Baker, Paris was her home long before it was

Dear newbornmuse,

Your point about not adding unnecessary commas before conjunctions is correct. However, not putting a comma before "and she remained" can change the meaning. The change in meaning is quite subtle.

You mention that you were looking for Modifier, Clause 1 and Clause 2. In this construction, there is nothing to suggest that the modifier cannot apply to BOTH Clause 1 and Clause 2. The comma makes the modifier apply to only Clause 1.

Let's read D without the comma:
Long
...

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