GMAT Sentence Correction (SC) | Re: Arctic terns, being true long-distance migrants

Arctic terns, being true long-distance migrants, they nest in coastal wetlands of northern Europe but fly south for thousands of miles to spend the European winters in Antarctica

The basic parallelism we need to search here for correct option is using thekeyword in the non-underlined part , i.e. fly
Contenders : (A),(C) & (E).
PoE : (A) : pronoun "they quot; is placed far away from "Arctic terns" to which it is referring. Also, the use of "being quot; is awkward here.
(C)
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