English grammar error-spotting (pronoun/number agreement in a coordinated antecedent): Read the sentence split into four parts (A–D) and locate the error; pick ‘‘No error’’ only if the whole sentence is correct. ‘‘The scientist must follow / his hunches and his data / wherever it may lead. / No error.’’

Given data

• Compound antecedent: ‘‘hunches’’ (plural) + ‘‘data’’ (treated as plural in careful usage)
• Anaphoric pronoun: ‘‘it’’ (singular)

Concept / Approach
A plural antecedent requires a plural pronoun and verb: ‘‘wherever they may lead.’’ Even if one treats ‘‘data’’ as a mass noun informally, the coordination with ‘‘hunches’’ keeps the reference plural.

Correction
‘‘… hunches and … data, wherever they may lead.’’

Verification
The clause now agrees in number and reads naturally.

Final Answer
wherever it may lead.