Recovery of Written-Off Bad Debt Steps:

• Identify the original write-off: Debit irrecoverable debts expense $450, credit receivables$450.
• On partial recovery of $100: Debit bank$100 to record cash inflow.
• Credit irrecoverable debts $100 to reverse part of the prior expense.
• This nets the irrecoverable debts account down by the recovered amount.

Why A is correct:

• Standard double-entry for bad debt recovery debits bank (asset increase) and credits irrecoverable debts (reduces expense per accounting principles).

Why the others are wrong:

• B: Incorrectly suggests debiting a recovery account while crediting irrecoverable debts, reversing the flow.
• C: Uses "debts recovered" as credit, but proper entry credits irrecoverable debts directly, not a separate recovery ledger.
• D: Reverses entries by debiting irrecoverable debts and crediting bank, which decreases cash incorrectly.

Final answer: A