Question:

<div class="solution"><p>Forced: f(2)=3, f(4)=5. Remaining: {1,3,5}\to{1,2,4} with f(1)≠2, f(3)≠4.</p><p>f⁻^1(2)=3: possible via f(1)=4,f(3)=2,f(5)=1 ✓</p><p>f⁻^1(2)=5: possible via f(1)=4,f(3)=1,f(5)=2 ✓</p><p>f⁻^1(2)=1: impossible (f(1)≠2)</p><p><strong>Answer: (B),(C)</strong></p><div class="trap-box"><strong>Trap:</strong> The biconditional restricts both even AND odd inputs.<div class="key-concept"><strong>Key Concept:</strong> Finite bijection -- lock forced values, distribute remainder under constraints