Identify the part of the sentence that contains an error: 'Neither of the two candidates / were qualified enough / to handle the responsibilities / of the airport safety officer.'

The subject 'Neither' is singular in construction, and when 'neither of' is followed by a plural noun, the verb still remains singular. Therefore, 'were qualified' should be replaced with 'was qualified'. The rule is that 'neither', 'either', 'each', 'every', and 'none' generally take singular verbs in formal English usage. The correct sentence reads: 'Neither of the two candidates was qualified enough to handle the responsibilities of the airport safety officer.' This is a standard subject-verb agreement rule tested frequently in competitive examinations.