Step 1: Understanding set-off.
Set-off under CPC allows defendant to claim an ascertained sum legally recoverable from plaintiff in same capacity.
Step 2: Case analysis.
- (A): The debts are mutual, ascertained, and between the same parties in same capacity → valid set-off.
- (B): Claim for damages in specific performance is unascertained and not liquidated → cannot be set-off.
Step 3: Conclusion.
Hence, only (A) is valid.