Error spotting (exam direction): Identify the erroneous part (A/B/C) — choose D if there is no error — 'If I were him, / I would have taught / those cheats a lesson. / No error.'

Given parts (A–D)
A. If I were him,B. I would have taughtC. those cheats a lesson.D. No error.

Concept/Approach (case after 'were'; tense consistency)
In formal English, after a linking verb ('were' in the subjunctive), the complement takes the subject case: 'If I were he.' Also, for a past unreal condition, the fully consistent form is 'If I had been he, I would have taught…'

Step-by-step correction
1) Case: 'him' → 'he' (formal).2) (Advanced) Tense harmony: 'If I had been he, I would have taught those cheats a lesson.'

Common pitfalls
Using object case after copular verbs; mixing present-subjunctive 'were' with past-perfect result clauses.

Final Answer
A — prefer 'If I were he,' (or fully: 'If I had been he,…').