Find the part of the sentence that contains an error: What the organization did not examine thoroughly enough (1)/ were not the scheme’s objectives themselves, (2)/ but the political consequences it (3)/ might have caused if carried out without wider agreement. (4)

The correct option is (b). In this sentence, the subject is the entire clause beginning with What: What the organization did not examine thoroughly enough. Such a whatclause functions as a singular subject in English. Therefore, it requires a singular verb. However, part (2) uses the plural verb phrase were not, which does not agree with the singular subject. The correct form should be was not: What the organization did not examine thoroughly enough was not the scheme’s objectives themselves, but the political consequences... Grammatical rule used: A clause used as a subject (especially a what-clause) generally takes a singular verb. Example (rule): What he said was surprising. (Not: were)