Sentence Correction (SC) | To meet the rapidly rising market demand for fish and seafood, supplie

Himikemcgarry ,GMATNinja ,GMATNinjaTwo ,

Sorry for bumping up this old thread, but I still don't quite understand how I could figure out what the "they" in choice D refers to - suppliers or fish? Also, are there any rules on figuring out the correct pronoun antecedent?
...

---