GMAT Sentence Correction (SC) | Yellow jackets number among the 900 or so species of the

Yellow jackets number among the 900 or so species of the world's social wasps,wasps living in a highly cooperative and organized society where they consist almost entirely of females—the queen and her sterile female workers.

A. wasps living in a highly cooperative and organized society where they consist almost entirely of - "they" refers to what, is not clear + "they" if referring to "wasps" will mean that "wasps consist almost entirely.." is incorrect,
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