Classify the following controls as preventive, detective, or corrective:
Periodic bank reconciliation.
Separation of cash and accounting records.
Maintaining backup copies of master and transaction files.
Pre-numbering of sales invoices.
Chart of accounts.
Retina scan before entering a sensitive R & D facility.
Resubmission of transactions for subsequent processing.
Internal auditor rechecking the debits and credits on the payment voucher.
Depositing all cash receipts intact.
Qualified accounting personnel.