The correct answer is A. Debtors account.
When a debt is written off, it is removed from the accounts and the debtor is considered to be a bad debt. If the debt is subsequently recovered, it is credited back to the debtors account. This is because the debt was originally recorded as a receivable, and when it is recovered, it should be recorded as a reduction in receivables.
Option B, Sales account, is incorrect because sales account is used to record sales revenue. Option C, Trading account, is incorrect because trading account is used to record the profit or loss from trading activities. Option D, Profit and loss account, is incorrect because profit and loss account is used to record all income and expenses, including bad debts.