GMAT Sentence Correction (SC) | Re: A majority of the international journalists surveyed view

Can someone explain when do we consider a pronoun ambiguous and when not? In this example, "they" can refer to either "a majority of journalists" or to "nuclear power stations" and it is far away from both. I understand that meaning wise it makes sense that it only refers to "nuclear power stations" --
but how and when do we make this judgement call? Very confusing that at times we are anal retentive about pronoun antecedents and sometimes not.

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